The United Nations Framework Convention on Climate Change (UNFCCC)
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The scientific work of the Intergovernmental Panel on Climate Change and much of the discussion of moral responsibility for addressing the challenge of global warming proceeds from the creation of the United Nations Framework Convention on Climate Change (UNFCC).
The goal of the UNFCCC, as articulated in Article 2, is the "stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system."
There is an important caveat, however. The primary goal should be promoted within the limits set by what is required for achieving other goals, such as food production, the need for time for adjustment of national economies, and especially, the needs for sustainable economic development.
The UNFCC thus endorsed the commitment to "common but differentiated responsibilities" among nations. While the UNFCCC conception of moral responsibility is open-ended, the underlying understanding of the oft-cited phrase is that the locus of moral responsibility should be nation-states working collaboratively, and in particular, the developed nations (Annex I countries) should take the lead, thereby allowing the lesser developed nations to pursue economic development. That framework was abandoned at the Durban conference in 2012, at the behest of the United States.
The goal of the UNFCCC, as articulated in Article 2, is the "stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system."
There is an important caveat, however. The primary goal should be promoted within the limits set by what is required for achieving other goals, such as food production, the need for time for adjustment of national economies, and especially, the needs for sustainable economic development.
The UNFCC thus endorsed the commitment to "common but differentiated responsibilities" among nations. While the UNFCCC conception of moral responsibility is open-ended, the underlying understanding of the oft-cited phrase is that the locus of moral responsibility should be nation-states working collaboratively, and in particular, the developed nations (Annex I countries) should take the lead, thereby allowing the lesser developed nations to pursue economic development. That framework was abandoned at the Durban conference in 2012, at the behest of the United States.
A Brief Chronology of Major Efforts Toward International Collaboration in Response to Climate Change
- 1988 - World Conference on the Changing Atmosphere in Toronto - recommends reducing GHG emissions by 20% by 2005 and it led to the creation of the Intergovernmental Panel on Climate Change (IPCC)
- 1990 - IPCC 1st Report - projected .3 C change in global temperature per decade (range of uncertainty of .2 - .5); uncertainty range was said to be due to difficulty in separating out the "background noise" of natural variability
- 1992 - Rio Earth Summit - produced the UN Convention on Climate Change (UNFCCC) and it elicited some early commitments of some nations to stabilize their emissions at 1990 levels by 2000
- 1995 2nd IPCC Report
- 1997 Kyoto Summit ended in the production of the Kyoto Protocol, which was not ratified by enough countries to take effect until 2005; the Protocol was set to expire in 2012 and the aim was to update and replace it
- 2001 3rd IPCC Report - concluded that most of the observed warming over the last 50 years was due to the increase in GHGs in the atmosphere; the US renounces the Protocol
- 2005 Russia signs on to the Kyoto Protocol and it takes effect
- 2007 4th IPCC Report - provided a range of scenarios: slow emission scenarios (1.8. C with a range of 1.1 - 2.9 C) and high emission scenarios (4.0 C. with a range of 2.4 - 6.4 C), an asserted a 90% probability that the warming trend was anthropogenic (human induced)
- 2009 Copenhagen Accord - called for limits of 2.0 C temperature rise above pre-industrial levels and for nations by the end of 2010 to set targets for 2020 reduction of emissions; it called for a cut of 50-80% of 1990 level emissions just to maintain the current level of climate disruption
- 2012 Durban Conference - Kyoto Protocol expired without a replacement treaty; Article 25 provided all the signatories an exit option, incurring no penalties, should they not meet their agreed upon targets; they exited at the end of this 17th international conference held under the framework of the UNFCCC
- 2012 Doha discussions. Nothing much happened: "no dates, no dollars" as the saying goes
- 2013-2014 5th IPCC Report
- 2015 The Paris Accord signed at the COP 21, where each nation committed to goals, known as "Intended Nationally Determined Contributions"
- 2018 The IPCC Special Report: Global Warming at 1.5 degrees
- 2019 The IPCC Special Report on Climate Change and Land Use
- 2020 - November 4 is the day that countries that wish to abandon their commitment to the Paris Accord can officially do so. That's the day after the United States presidential election...
- 2021-2022 The 6th IPCC Report drafts will circulate and the final report is scheduled for July, 2022.
To Understand the Greenhouse Effect, Think of the "Bathtub Effect"
Source: http://www.epa.gov/climatechange/science/causes.html
One of the most widely employed visual images for explaining how the accumulation of greenhouse gases in the atmosphere works is that of a clogged bathtub. Andrew Revkin in a New York Times blog post summarizes it as follows,
"Think of the atmosphere as a bathtub with a partially opened drain. Carbon dioxide and other greenhouse gases from burning fuels and destruction of forests – the faucet – are flowing into the tub twice as fast as they are being absorbed by plants and the ocean – the drain. Meanwhile, the “sinks” – forests and oceans that absorb greenhouse gases – are becoming saturated, so the drain is clogged up."
Four Conclusions for Which We Have Considerable Confidence
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- Since the Industrial Revolution (circa 1850) the accumulation of greenhouse gases (GHGs) in the atmosphere has grown dramatically and faster than they have been radiated away from the planet and into the solar system
- the accumulation of GHGs is causally related to global temperature rise
- human activities since 1850 have increased the accumulation of GHGS
- the even more dramatic growth in GHGs since 1950 parallels the growth in global population - from 2.5 billion in 1950 to over 7 billion now - and the spread of industrialization, as the graphic to the right reflects
- See, e.g., Working Group 1, (AR 4) Summary for Policy Makers, The Physical Basis
- Source of graphic: Carbon Dioxide Information Analysis Center (CDIAC)
The 5th Assessment Report. You can read the Summary for Policymakers here.
Here are some highlights and points of difference with the 2007 AR4 Report.
A major finding: “It is extremely likely that human influence on climate caused more than half of the observed increase in global average surface temperature from 1951 to 2010.” New research examining changes, not only at the Earth’s surface but within the oceans, and through the depth of the atmosphere and in other parts of the climate system. This new research allowed the IPCC to increase its confidence since its last 2007 AR4 report that humans bear most of the responsibility, and it now says it is extremely likely (above 95%) that human influence has been the dominant cause of the observed warming since the mid-20th century.
The AR4 report, by contrast, concluded that the chances were at least 90 percent that human activities were the principal cause. The reference to 95% has a precise scientific meaning. It is equivalent to the certainty that cigarettes cause lung cancer.
Also, there is one methodological difference and that change made a difference in its findings: The 2007 report relied upon what they called emissions scenarios; the 2013-14 reports speak of RCPs, representative concentration pathways. The previous report largely ruled out any outcome in which the atmospheric temperature would fall below 3.6 degrees Fahrenheit.
The new report says the atmospheric temperature rise could be as low as 2.7 degrees. That change reflects the wider range of consensus estimates that prevailed from 1979 to 2007. In other words, the top of the range of uncertainty remained at 4.5C, but the lower bound dropped from 2C to 1.5C. The 1.5 – 4.5 range is identical to that in the very first IPCC report in 1990.
However, the AR5 report made it clear that given current trends, the lower range projections are not likely. The report found that it was still technically possible to limit global warming to an internationally agreed upper bound of 3.6 degrees Fahrenheit, or 2 degrees Celsius, above the preindustrial level, but that outcome would require a significant reversal of current trends. To do so, we would need to emit half as much greenhouse gas for the remainder of this century as we’ve already emitted over the past 250 years. More precisely, deep emissions cuts between 40 and 70 percent are needed between 2010 and 2050, with emissions “falling towards zero or below” by 2100.
If present trends continue the level of greenhouse gas concentration could double in a matter of decades. They note that the evidence suggests that if carbon dioxide doubles an increase above 5 degrees Fahrenheit is more likely. Were we to experience 7.2 degrees F of warming above preindustrial temperatures by the end of the century, there will be “substantial species extinction, global and regional food insecurity, [and] consequential constraints on common human activities.”
The different consequences of representative RCPs are reflected in the graphic, starting with RCP2.6 [the low emissions projection] up through RCP8.5 [the high emissions projection] by 2100. The high emissions outcome is that the combination of high temperature and humidity in some regions, for parts of the year, will compromise normal activities, including growing food or working outdoors (high confidence).
You can read more about the scenarios in AR 4 in discussions below on this page.
Here are some highlights and points of difference with the 2007 AR4 Report.
A major finding: “It is extremely likely that human influence on climate caused more than half of the observed increase in global average surface temperature from 1951 to 2010.” New research examining changes, not only at the Earth’s surface but within the oceans, and through the depth of the atmosphere and in other parts of the climate system. This new research allowed the IPCC to increase its confidence since its last 2007 AR4 report that humans bear most of the responsibility, and it now says it is extremely likely (above 95%) that human influence has been the dominant cause of the observed warming since the mid-20th century.
The AR4 report, by contrast, concluded that the chances were at least 90 percent that human activities were the principal cause. The reference to 95% has a precise scientific meaning. It is equivalent to the certainty that cigarettes cause lung cancer.
Also, there is one methodological difference and that change made a difference in its findings: The 2007 report relied upon what they called emissions scenarios; the 2013-14 reports speak of RCPs, representative concentration pathways. The previous report largely ruled out any outcome in which the atmospheric temperature would fall below 3.6 degrees Fahrenheit.
The new report says the atmospheric temperature rise could be as low as 2.7 degrees. That change reflects the wider range of consensus estimates that prevailed from 1979 to 2007. In other words, the top of the range of uncertainty remained at 4.5C, but the lower bound dropped from 2C to 1.5C. The 1.5 – 4.5 range is identical to that in the very first IPCC report in 1990.
However, the AR5 report made it clear that given current trends, the lower range projections are not likely. The report found that it was still technically possible to limit global warming to an internationally agreed upper bound of 3.6 degrees Fahrenheit, or 2 degrees Celsius, above the preindustrial level, but that outcome would require a significant reversal of current trends. To do so, we would need to emit half as much greenhouse gas for the remainder of this century as we’ve already emitted over the past 250 years. More precisely, deep emissions cuts between 40 and 70 percent are needed between 2010 and 2050, with emissions “falling towards zero or below” by 2100.
If present trends continue the level of greenhouse gas concentration could double in a matter of decades. They note that the evidence suggests that if carbon dioxide doubles an increase above 5 degrees Fahrenheit is more likely. Were we to experience 7.2 degrees F of warming above preindustrial temperatures by the end of the century, there will be “substantial species extinction, global and regional food insecurity, [and] consequential constraints on common human activities.”
The different consequences of representative RCPs are reflected in the graphic, starting with RCP2.6 [the low emissions projection] up through RCP8.5 [the high emissions projection] by 2100. The high emissions outcome is that the combination of high temperature and humidity in some regions, for parts of the year, will compromise normal activities, including growing food or working outdoors (high confidence).
You can read more about the scenarios in AR 4 in discussions below on this page.
IPPC 4th Assessment Reports (AR4): A Primary Source for Detailed Information
Click link for all 4 documents
The 4 IPCC reports (1990, 1995, 2001, 2007) are massive undertakings, complete with appendices and supplementary technical papers.
All 4 IPCC reports are divided into 3 sections, each produced by a Working Group:
All 3 Working Group reports from the 4th Assessment (2007), plus a Synthesis Report (shown in the image above) can be obtained from the IPCC website. The IPCC website also provides a Summary for Policymakers outlining some of the key findings from the 4th Assessment . The report is available in several languages.
All 4 IPCC reports are divided into 3 sections, each produced by a Working Group:
- discussion of the basics of climate science, the predictive models, matters of scientific uncertainty, an explanation of the range of likely global temperature rise predictions, and some indicators of the Panel's confidence level in many of its key findings
- discussions of expected effects of a rise in global atmospheric temperature, including its impact on desertification and loss of available groundwater, extreme weather events, regionally differential impact on temperature and rainfall, the impact on communicable disease, loss of coastline and other consequences of sea-level rise, and more
- discussion of possible mechanisms for mitigation - restraining the rise in atmospheric temperature to the lower range of estimates - and adaptation - strategies for coping with or reducing the adverse effects of global warming
All 3 Working Group reports from the 4th Assessment (2007), plus a Synthesis Report (shown in the image above) can be obtained from the IPCC website. The IPCC website also provides a Summary for Policymakers outlining some of the key findings from the 4th Assessment . The report is available in several languages.
Structural Uncertainty and Confidence Levels
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Climate science is riddled with scientific uncertainties and estimates of the range of uncertainty are important to the understanding of the conclusions of any study or summary of existing evidence. All estimates of scientific uncertainty are intrinsically statements intended to describe the limits to knowledge. The IPCC 4th Assessment (Section 1.6) notes that "uncertainties can be classified in several different ways according to their origin." The Fourth Assessment Report draws a distinction between:
The distinction is not an easy one for non-scientists to grasp, but a careful reading of the IPPC Report demands some understanding of the basic idea behind the distinction. Let's begin with the problem of structural uncertainties.
Structural uncertainties arise from "an incomplete understanding of the processes that control particular results." So for example, climate forcings such as cloud formations (see NASA entry above) are processes believed to have significant impact on global warming, but the processes by which the expected results are obtained are poorly understood. Thus, we need some statement of the confidence level scientists attach to the judgments about those processes.
The IPCC Report expresses levels of confidence in the understanding of various processes using the terminology of very high confidence, high confidence, medium confidence, low confidence, and very low confidence.
To appreciate structural uncertainties and differences in levels of confidence see the chart above. The horizontal bar shows confidence levels in our understanding of various types of radiative forcings. As you move rightward on the horizontal axis, you can see that for 8 of the 12 sources of radiative forcing the Level of Understanding fall into the "very low" category. But that does not undermine the high confidence scientists have about the fundamental role of greenhouse gases.
- (i) levels of confidence in scientific understanding (structural uncertainties), and
- (ii) the likelihoods of specific results (value uncertainties)
The distinction is not an easy one for non-scientists to grasp, but a careful reading of the IPPC Report demands some understanding of the basic idea behind the distinction. Let's begin with the problem of structural uncertainties.
Structural uncertainties arise from "an incomplete understanding of the processes that control particular results." So for example, climate forcings such as cloud formations (see NASA entry above) are processes believed to have significant impact on global warming, but the processes by which the expected results are obtained are poorly understood. Thus, we need some statement of the confidence level scientists attach to the judgments about those processes.
The IPCC Report expresses levels of confidence in the understanding of various processes using the terminology of very high confidence, high confidence, medium confidence, low confidence, and very low confidence.
To appreciate structural uncertainties and differences in levels of confidence see the chart above. The horizontal bar shows confidence levels in our understanding of various types of radiative forcings. As you move rightward on the horizontal axis, you can see that for 8 of the 12 sources of radiative forcing the Level of Understanding fall into the "very low" category. But that does not undermine the high confidence scientists have about the fundamental role of greenhouse gases.
Value Uncertainties and the Likelihood of Events Distinguished from Structural Uncertainty
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Value uncertainties is second major type of uncertainty. The term is used to express estimates of the likelihood of specific results or outcomes. Value uncertainties, as they are called, arise from the "incomplete determination of particular outcomes or results, for example, when data are inaccurate or not fully representative of the phenomenon of interest... Value uncertainties are generally estimated using statistical techniques and expressed probabilistically."
Estimates of a likely result are expressed as Virtually Certain (> 99% probability); Extremely likely (> 95% probability); Very likely (> 90% probability); Likely (> 66% probability); More likely than not (> 50% probability); About as likely as not (33 to 66% probability); Unlikely (< 33% probability); Very unlikely (< 10% probability); Extremely unlikely (< 5% probability); and Exceptionally unlikely (< 1% probability).
The chart above from the IPCC's AR4 Summary for Policy Makers (p. 9) shows some of the estimates of likelihood of various types of changes in weather events. Some are very likely (> 90% probability), while others are likely (> 66% probability), and some are either counted as likely or very likely only for certain areas.
Estimates of a likely result are expressed as Virtually Certain (> 99% probability); Extremely likely (> 95% probability); Very likely (> 90% probability); Likely (> 66% probability); More likely than not (> 50% probability); About as likely as not (33 to 66% probability); Unlikely (< 33% probability); Very unlikely (< 10% probability); Extremely unlikely (< 5% probability); and Exceptionally unlikely (< 1% probability).
The chart above from the IPCC's AR4 Summary for Policy Makers (p. 9) shows some of the estimates of likelihood of various types of changes in weather events. Some are very likely (> 90% probability), while others are likely (> 66% probability), and some are either counted as likely or very likely only for certain areas.
Range of Temperature Rise Projections and The Underlying Assumptions of the 6 Scenarios
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The 4th IPCC Assessment Climate provides temperature rise predictions under 6 scenarios. The Report notes that the "best estimates and likely ranges for global average surface air warming for six scenarios are given in this assessment and are shown in the figure SPM.5 [from the Report reproduced on the left].
The best estimate for the low scenario (B1) is 1.8°C (likely range is 1.1°C to 2.9°C), and the best estimate for the high scenario (A1FI) is 4.0°C (likely range is 2.4°C to 6.4°C).
The best estimate for the low scenario (B1) is 1.8°C (likely range is 1.1°C to 2.9°C), and the best estimate for the high scenario (A1FI) is 4.0°C (likely range is 2.4°C to 6.4°C).
Understanding the 6 Scenarios in AR4
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The 6 scenarios are distinguished primarily by the following assumptions (quoted directly from AR4).
- "The A1 storyline and scenario family describes a future world of very rapid economic growth, global population that peaks in mid-century and declines thereafter, and the rapid introduction of new and more efficient technologies... The three A1 groups are distinguished by their technological emphasis: fossil-intensive (A1FI), non-fossil energy sources (A1T) or a balance across all sources (A1B) (where balanced is defined as not relying too heavily on one particular energy source, on the assumption that similar improvement rates apply to all energy supply and end use technologies)."
- "The B1 storyline and scenario family describes a convergent world with the same global population, that peaks in mid-century and declines thereafter, as in the A1 storyline, but with rapid change in economic structures toward a service and information economy, with reductions in material intensity and the introduction of clean and resource-efficient technologies."
- "The B2 storyline and scenario family describes a world in which the emphasis is on local solutions to economic, social and environmental sustainability. It is a world with continuously increasing global population, at a rate lower than A2, intermediate levels of economic development, and less rapid and more diverse technological change than in the B1 and A1 storylines."
Business-As-Usual Scenario (IS92a)
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Another scenario that is often referred to in the literature, especially in the early years after the adoption of the UNFCCC, is the IS92a scenario. It is often referred to in climate change modeling and impact studies as the "business-as- usual" scenario. The original meaning of the "business-as-usual" phrase identified a range of energy emissions scenarios found by the 1st IPCC Assessment to be representative of the scenarios available in the open literature at that time. Since then, the focus of the technical literature has been on the 4th Assessment's 6 scenarios, but business-as-usual remains a common way of describing more generally the continuation (and likely expansion) of historical carbon emissions without any significant annual reductions.
The IPCC 4th Assessment Report (1.4) notes that the move to the current 6 scenarios was motivated by some of the weaknesses of the IS92a scenario. In particular, range of CO2 intensities of energy (CO2 emissions per unit energy) was represented and no scenario reflected the likely prospect that the 21st century would see a significant closure in the income gap between developed and developing countries, causing historical patterns of emissions to understate what we have very good reason to expect.
The IPCC 4th Assessment Report (1.4) notes that the move to the current 6 scenarios was motivated by some of the weaknesses of the IS92a scenario. In particular, range of CO2 intensities of energy (CO2 emissions per unit energy) was represented and no scenario reflected the likely prospect that the 21st century would see a significant closure in the income gap between developed and developing countries, causing historical patterns of emissions to understate what we have very good reason to expect.
Other Uncertainties: Emission Projections, the Stochastic Nature of the Science, & Measurement Errors
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For a discussion of the distinctions among various types of uncertainty in climate science, see the Australian Parliament's Climate Science Website, noting uncertainties that fall under the IPCC headings of structural uncertainties and value uncertainty, as well as three other categories of uncertainty: "uncertainty in assumptions about future socioeconomic scenarios and emission trajectories; inherent limitations to the representation of many of these processes due to their stochastic nature, e.g. the chaotic nature of the climate system and indeterminacy of human behaviour; errors in observations due to instrumental limitations; or errors in observations due to insufficient sampling."
The graphic above depicts the emissions accumulations under each of the 6 scenarios (plus IS92a) that rely heavily on assumptions about future socioeconomic factors and emissions trajectories.The 4th Assessment Report (1.6) also discusses uncertainties that are inherent to the types of causal relationships being modeled. They "arise in systems that are either chaotic or not fully deterministic in nature and this also limits our ability to project all aspects of climate change."
The IPCC 4th Report (1.6) notes the following regarding uncertainty simply due to error: "Uncertainties associated with ‘random errors’ have the characteristic of decreasing as additional measurements are accumulated, whereas those associated with ‘systematic errors’ do not. In dealing with climate records, considerable attention has been given to the identification of systematic errors or unintended biases arising from data sampling issues and methods of analysing and combining data. Specialised statistical methods based on quantitative analysis have been developed for the detection and attribution of climate change and for producing probabilistic projections of future climate parameters."
The graphic above depicts the emissions accumulations under each of the 6 scenarios (plus IS92a) that rely heavily on assumptions about future socioeconomic factors and emissions trajectories.The 4th Assessment Report (1.6) also discusses uncertainties that are inherent to the types of causal relationships being modeled. They "arise in systems that are either chaotic or not fully deterministic in nature and this also limits our ability to project all aspects of climate change."
The IPCC 4th Report (1.6) notes the following regarding uncertainty simply due to error: "Uncertainties associated with ‘random errors’ have the characteristic of decreasing as additional measurements are accumulated, whereas those associated with ‘systematic errors’ do not. In dealing with climate records, considerable attention has been given to the identification of systematic errors or unintended biases arising from data sampling issues and methods of analysing and combining data. Specialised statistical methods based on quantitative analysis have been developed for the detection and attribution of climate change and for producing probabilistic projections of future climate parameters."
Uncertainty: Climate Sensitivity and the Magnitude and Distribution of Effects
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The average global temperature rise for its land surface area at any given level of the accumulation of GHGs in the atmosphere depends on the accuracy of assumptions regarding climate sensitivity. The IPCC 4th Assessment calculation of climate sensitivity links a 3°C warming due to a doubling of CO2, with a 90 percent confidence level of 2°C to 4.5°C warming (see graph to the left). Thus we see the measure of uncertainty in the familiar linkage between estimates of parts per million GHG concentrations and the expected temperature rise associated with each estimate. Accordingly, the temperature predictions are expressed in ranges.
For example, the best estimate for the low scenario (B1) is 1.8°C (likely range is 1.1°C to 2.9°C), and for a concentration of 450ppm the estimated rise is 2°C. But a concentration of 450ppm could result in a greater or lesser temperature rise. See the IPCC AR4 Synthesis, p. 67, table 5.1, where In fact, for the estimated range for a GHG intensity between 445 and 490 ppm CO2e, the likely rise in temperature will be between 2° and 2.4°C.
Equally important is the fact that not all geographic regions are the same in climate sensitivity. It is generally assumed that the northern latitudes are more sensitive to GHC concentrations, resulting a larger increase in land surface temperatures than we can expect in southern latitudes at the same level of GHG concentration.
Also important is the fact that greater climate sensitivity does not equate automatically with greater adverse impact. In fact, the opposite relationship is the expectation, but only up to a point. At the lower end of the 6 climate change scenarios, where temperature rises are comparatively modest, some northern countries that are more sensitive to any given carbon concentration may benefit (in some respects) from their greater increase in land surface temperatures. Canada is the standard example, and the prospect for increased agricultural yield is the expected benefit. But countries clustered around the Equator, as well as low-lying coastal areas and islands, are more vulnerable to catastrophic harms, even at the lower end of the projected average global temperature rises. For more on these topics, see Climate Roulette.
For example, the best estimate for the low scenario (B1) is 1.8°C (likely range is 1.1°C to 2.9°C), and for a concentration of 450ppm the estimated rise is 2°C. But a concentration of 450ppm could result in a greater or lesser temperature rise. See the IPCC AR4 Synthesis, p. 67, table 5.1, where In fact, for the estimated range for a GHG intensity between 445 and 490 ppm CO2e, the likely rise in temperature will be between 2° and 2.4°C.
Equally important is the fact that not all geographic regions are the same in climate sensitivity. It is generally assumed that the northern latitudes are more sensitive to GHC concentrations, resulting a larger increase in land surface temperatures than we can expect in southern latitudes at the same level of GHG concentration.
Also important is the fact that greater climate sensitivity does not equate automatically with greater adverse impact. In fact, the opposite relationship is the expectation, but only up to a point. At the lower end of the 6 climate change scenarios, where temperature rises are comparatively modest, some northern countries that are more sensitive to any given carbon concentration may benefit (in some respects) from their greater increase in land surface temperatures. Canada is the standard example, and the prospect for increased agricultural yield is the expected benefit. But countries clustered around the Equator, as well as low-lying coastal areas and islands, are more vulnerable to catastrophic harms, even at the lower end of the projected average global temperature rises. For more on these topics, see Climate Roulette.
Numerical Targets - 350ppm, 450ppm, 550ppm?
image is the logo of 350.org
There are several ways of expressing GHG emissions targets for which we should aim in order to avoid dangerous climate change consequences.
Parts per million (ppm): The Stern Report in 2006 called for a stabilization of atmospheric CO2 concentrations of 550ppm by 2050. Initial US policy statements echoed that target, but very few now accept that figure as low enough to avoid any reasonable construal of the UNFCCC's injunction to avoid "dangerous anthropogenic interference with the climate system."
NASA's compilation of trends and key indicators sets the current estimate of atmospheric carbon concentration at 393 ppm.
CO2 equivalent (CO2e): The current measure and stabilization targets are sometimes expressed as the CO2 equivalent (CO2e) CO2e is a measure designed to take into account other greenhouse gases (GHGs) — such as methane — that also contribute to climate change. The CO2e estimate is meant to be more encompassing, but it is also a somewhat more difficult calculation to make inasmuch as it requires incorporation of estimates of factors such as the extent to which these other GHGs remain in the atmosphere compared to CO2. Most targets and estimates of current accumulations use the simpler CO2 calculation.
Why 350?: The case for the 350ppm arises from the work of many of the leading climate scientists - for example, James Hansen, et al Target atmospheric CO2: Where should humanity aim?. This is the number that they say is the safe upper limit for carbon dioxide levels in the Earth's atmosphere, and the goal of the proponents of that target is to steer a course back to that safer level as soon as possible in order to avoid the most severe effects of global warming.
1.5 degrees C.: 350ppm is also the goal set by Bill McKibben's organization, 350.org. (see logo on the right), and the Alliance of Small Island States (AOSIS) also endorse a ceiling of 1.5 degrees C. above pre-industrial averages inasmuch as it is commonly assumed to be the rough equivalent of the 350ppm target. The statement of the AOSIS position is contained in their document "1.5 to Stay Alive."
450ppm, 2 degrees C., or I Trillion metric tons: The goal established by the Copenhagen Accord is 450 ppm, or approximately 2 degrees C above pre-industrial temperature averages. Another way to express targets in this general range is to identify a maximum atmospheric accumulation of 1 trillion metric tons of CO2. Here too, the linkage among alternative ways of identifying the target is somewhat loose. Most scientists say that staying under the 1 Trillion ton ceiling only gives us a 50% chance of staying under the 2 degree C target. By most calculations that leaves less than .5 Metric tons left to emit before entering the danger zone of a 2 degree temperature rise. The current estimate of metric tons is tracked by Oxford scientists at trillionthtonne.org. We are more than half way there and the current estimate is that, based on emissions levels of the last 20 years, we will emit the 1 Trillionth ton sometime in 2043.
Parts per million (ppm): The Stern Report in 2006 called for a stabilization of atmospheric CO2 concentrations of 550ppm by 2050. Initial US policy statements echoed that target, but very few now accept that figure as low enough to avoid any reasonable construal of the UNFCCC's injunction to avoid "dangerous anthropogenic interference with the climate system."
NASA's compilation of trends and key indicators sets the current estimate of atmospheric carbon concentration at 393 ppm.
CO2 equivalent (CO2e): The current measure and stabilization targets are sometimes expressed as the CO2 equivalent (CO2e) CO2e is a measure designed to take into account other greenhouse gases (GHGs) — such as methane — that also contribute to climate change. The CO2e estimate is meant to be more encompassing, but it is also a somewhat more difficult calculation to make inasmuch as it requires incorporation of estimates of factors such as the extent to which these other GHGs remain in the atmosphere compared to CO2. Most targets and estimates of current accumulations use the simpler CO2 calculation.
Why 350?: The case for the 350ppm arises from the work of many of the leading climate scientists - for example, James Hansen, et al Target atmospheric CO2: Where should humanity aim?. This is the number that they say is the safe upper limit for carbon dioxide levels in the Earth's atmosphere, and the goal of the proponents of that target is to steer a course back to that safer level as soon as possible in order to avoid the most severe effects of global warming.
1.5 degrees C.: 350ppm is also the goal set by Bill McKibben's organization, 350.org. (see logo on the right), and the Alliance of Small Island States (AOSIS) also endorse a ceiling of 1.5 degrees C. above pre-industrial averages inasmuch as it is commonly assumed to be the rough equivalent of the 350ppm target. The statement of the AOSIS position is contained in their document "1.5 to Stay Alive."
450ppm, 2 degrees C., or I Trillion metric tons: The goal established by the Copenhagen Accord is 450 ppm, or approximately 2 degrees C above pre-industrial temperature averages. Another way to express targets in this general range is to identify a maximum atmospheric accumulation of 1 trillion metric tons of CO2. Here too, the linkage among alternative ways of identifying the target is somewhat loose. Most scientists say that staying under the 1 Trillion ton ceiling only gives us a 50% chance of staying under the 2 degree C target. By most calculations that leaves less than .5 Metric tons left to emit before entering the danger zone of a 2 degree temperature rise. The current estimate of metric tons is tracked by Oxford scientists at trillionthtonne.org. We are more than half way there and the current estimate is that, based on emissions levels of the last 20 years, we will emit the 1 Trillionth ton sometime in 2043.
What has to be Done to Stay Below 450ppm, and If We Do, What's the Impact on Standard of Living?
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What is required in order to stay below the 450ppm threshold?: In order to stabilize at 450ppm at around 2050, global annual emissions will have to decline rather substantially, widely estimated to require a cut of around 50-80% of 2000 levels.
To keep global warming down to an increase of 2°C, the World Bank calculates, would cost $140 billion to $675 billion a year in developing countries, plus another $75 billion annual cost of adapting to global warming. For some more detailed estimates developed in line with differing sets of assumptions, see the World Bank's report, The Cost to Developing Countries of Adapting to Climate Change.
Recent estimates of global average GDP reduction are 1–4% if the emissions of CO2 are sufficient to stabilize the concentration in the atmosphere at 450 ppm (see graph above).
There is another way of looking at the sacrifice that might be required. In 2000, emissions per person (in metric tons) was just below 4 T per person with a global population of 6 billion. For a useful point of reference, the figure for the US is around 20 tons per person, while the metric ton per person estimate for China has already surpassed the 2000 global average.
The projected global population for 2050 is 9 billion. To cut annual global emissions by 2050 by 50-80%, while lesser developed nations greatly increase their rates of emission, and the global population increases by 50% is a very tall order. The required global per capita emissions would have to drop from the current global average of 4 tons that we find, for example in China, to somewhere between 1.33-1.5 tons.
What is the potential Impact on Standard of Living if we stay below 450ppm?: If (as some have argued) everyone in the world proceeded under an agreement assigning equal per capita rights to emit on the way to the target, absent enormous gains in energy efficiency, Darrel Moellendorf points out, very few people on the planet would have the standard of living now enjoyed by the portion of the world's population ranked in the top half of the World Bank's Human Development Index (HDI).
That said, Norway currently supports an HDI that surpasses the US but with around half the per capita emissions. The correlation between per capita emissions and standard of living is an imperfect one, with much room for improvement in the former without degradation of the latter, but the behavioral adjustment required of the world's users of the most carbon-intensive technology would have to change rather fundamentally and rather soon in the direction of a radically decarbonized lifestyle in order to meet even the 450 target.
To keep global warming down to an increase of 2°C, the World Bank calculates, would cost $140 billion to $675 billion a year in developing countries, plus another $75 billion annual cost of adapting to global warming. For some more detailed estimates developed in line with differing sets of assumptions, see the World Bank's report, The Cost to Developing Countries of Adapting to Climate Change.
Recent estimates of global average GDP reduction are 1–4% if the emissions of CO2 are sufficient to stabilize the concentration in the atmosphere at 450 ppm (see graph above).
There is another way of looking at the sacrifice that might be required. In 2000, emissions per person (in metric tons) was just below 4 T per person with a global population of 6 billion. For a useful point of reference, the figure for the US is around 20 tons per person, while the metric ton per person estimate for China has already surpassed the 2000 global average.
The projected global population for 2050 is 9 billion. To cut annual global emissions by 2050 by 50-80%, while lesser developed nations greatly increase their rates of emission, and the global population increases by 50% is a very tall order. The required global per capita emissions would have to drop from the current global average of 4 tons that we find, for example in China, to somewhere between 1.33-1.5 tons.
What is the potential Impact on Standard of Living if we stay below 450ppm?: If (as some have argued) everyone in the world proceeded under an agreement assigning equal per capita rights to emit on the way to the target, absent enormous gains in energy efficiency, Darrel Moellendorf points out, very few people on the planet would have the standard of living now enjoyed by the portion of the world's population ranked in the top half of the World Bank's Human Development Index (HDI).
That said, Norway currently supports an HDI that surpasses the US but with around half the per capita emissions. The correlation between per capita emissions and standard of living is an imperfect one, with much room for improvement in the former without degradation of the latter, but the behavioral adjustment required of the world's users of the most carbon-intensive technology would have to change rather fundamentally and rather soon in the direction of a radically decarbonized lifestyle in order to meet even the 450 target.
What if We Don't Stay Below 450ppm?
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The World Bank, through the International Bank for Reconstruction and Development, endorses the 450ppm target, but it note the following likely consequences:
"Between 100 million and 400 million more people could be at risk of hunger. And 1billion to 2 billion more people may no longer have enough water to meet their needs." (Source: Development and Climate Change, p. 5. More specifically, the report indicates that "developing countries are the most vulnerable to the negative impacts of climate change, and that they face 75 to 80 percent of the potential damage from climate change... global warming of more than 2°C above pre-industrial temperatures—an increase that will be extremely difficult to avoid—more than a billion people could face water scarcity, 15 to 30 percent of species worldwide could be doomed to extinction, and hunger will rise, particularly in tropical countries."
The chart above shows recent estimates of economic impact a temperature increase of 1.92°C compared to pre-industrial levels in 2050. Northern Europe is expected to slightly benefit (+0.18%), while Southern and Eastern Europe are expected to suffer from the climate change scenario under analysis (-0.15% and -0.21% respectively). Most vulnerable countries are the less developed regions, such as South Asia, South-East Asia, North Africa and Sub-Saharan Africa.
Rajendra Pachauri, head of the IPCC, has said that 450 ppm would bring with it disaster: "The Maldive Islands, which are barely a meter above sea level, most of those islands, extensive areas of Bangladesh, a country of 160 million people, and there are other regions, including parts of the U.S., that will be completely devastated. And therefore even the 2-degree limit that we’re talking about, which corresponds to say about 450 parts per million, is pretty bad news."
A November 2012 study, Turn Down the Heat, prepared by the Potsdam Institute for Climate Impact Research and
Climate Analytics at the direction of the World Bank Group examined the global consequences of a 4 degree increase. The study attempted to outline a range of risks, focusing on developing countries and especially the poor. The sobering conclusion is that if the more substantial commitments to reduce GHGs are not met in the near future the world could see the 4 degree increase by the 2060s. They note that it is not even clear that human populations have the capacity to adapt to a world so fundamentally altered as ours would be at that temperature.
"Between 100 million and 400 million more people could be at risk of hunger. And 1billion to 2 billion more people may no longer have enough water to meet their needs." (Source: Development and Climate Change, p. 5. More specifically, the report indicates that "developing countries are the most vulnerable to the negative impacts of climate change, and that they face 75 to 80 percent of the potential damage from climate change... global warming of more than 2°C above pre-industrial temperatures—an increase that will be extremely difficult to avoid—more than a billion people could face water scarcity, 15 to 30 percent of species worldwide could be doomed to extinction, and hunger will rise, particularly in tropical countries."
The chart above shows recent estimates of economic impact a temperature increase of 1.92°C compared to pre-industrial levels in 2050. Northern Europe is expected to slightly benefit (+0.18%), while Southern and Eastern Europe are expected to suffer from the climate change scenario under analysis (-0.15% and -0.21% respectively). Most vulnerable countries are the less developed regions, such as South Asia, South-East Asia, North Africa and Sub-Saharan Africa.
Rajendra Pachauri, head of the IPCC, has said that 450 ppm would bring with it disaster: "The Maldive Islands, which are barely a meter above sea level, most of those islands, extensive areas of Bangladesh, a country of 160 million people, and there are other regions, including parts of the U.S., that will be completely devastated. And therefore even the 2-degree limit that we’re talking about, which corresponds to say about 450 parts per million, is pretty bad news."
- For the IPPC discussion of targets, stabilization models, and assumptions, see the IPCC's Synthesis Report for AR4 .
- For a provocative discussion by Bill McKibben on the target debate, see his essay in the August 2, 2012 issue of Rolling Stone, "Global Warming's Terrifying New Math."
A November 2012 study, Turn Down the Heat, prepared by the Potsdam Institute for Climate Impact Research and
Climate Analytics at the direction of the World Bank Group examined the global consequences of a 4 degree increase. The study attempted to outline a range of risks, focusing on developing countries and especially the poor. The sobering conclusion is that if the more substantial commitments to reduce GHGs are not met in the near future the world could see the 4 degree increase by the 2060s. They note that it is not even clear that human populations have the capacity to adapt to a world so fundamentally altered as ours would be at that temperature.
What Americans Believe About Climate Science
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The Yale Project on Climate Change has been surveying public attitudes and beliefs regarding global warming and they have found six distinct clusters of public sentiment, which they label as the Alarmed, the Concerned, the Cautious, the Doubtful, and the Disengaged, and the Dismissive. The most recent report dated July 12, 2012 and can be downloaded from their website in pdf format.
According to a July, 2012 Washington Post-Stanford University poll, climate change no longer ranks first on the list of what Americans see as the world’s biggest environmental problem. It has been surpassed by water and air pollution. While the poll indicated that the public shows no significant signs of backing away from the idea that government should take action on the issue, about "a quarter of the public trusts what scientists say about the issue “completely” or “a lot,” while 35 percent, trust scientists only a little or not at all. Thirty-eight percent trust scientific opinions a moderate amount."
In a poll taken July 12-16, 2012, Bloomberg Businessweek reports that 70 percent of US respondents said they think the climate is changing, compared with 65 percent in a similar poll in March. The pollsters speculate that record heat waves, drought and catastrophic wildfires, rather than belief based in scientific models is responsible for the shift. Climate deniers fell from 22% to 15% in that same period. By contrast, only 2 per cent of Canadians who responded to an opinion poll in conducted almost a month later believe climate change is not occurring.
According to a July, 2012 Washington Post-Stanford University poll, climate change no longer ranks first on the list of what Americans see as the world’s biggest environmental problem. It has been surpassed by water and air pollution. While the poll indicated that the public shows no significant signs of backing away from the idea that government should take action on the issue, about "a quarter of the public trusts what scientists say about the issue “completely” or “a lot,” while 35 percent, trust scientists only a little or not at all. Thirty-eight percent trust scientific opinions a moderate amount."
In a poll taken July 12-16, 2012, Bloomberg Businessweek reports that 70 percent of US respondents said they think the climate is changing, compared with 65 percent in a similar poll in March. The pollsters speculate that record heat waves, drought and catastrophic wildfires, rather than belief based in scientific models is responsible for the shift. Climate deniers fell from 22% to 15% in that same period. By contrast, only 2 per cent of Canadians who responded to an opinion poll in conducted almost a month later believe climate change is not occurring.
Uncertainty and Skepticism: Sorting Fact from Fiction with Regard to Problems of Uncertainty
For a discussion that attempts the daunting task of providing an accessible overview of the different types of uncertainty in climate science and what we should make of each, see the Section entitled "Uncertainty and Scepticism" in the Australian Parliament's Climate Science Website.
The overarching aim of this specific section of the Climate Science Website is to debunk some mistaken beliefs about scientific uncertainty and how some critics have argued that the most basic claims made by climate scientists are undermined. Here is their list of myths:
The overarching aim of this specific section of the Climate Science Website is to debunk some mistaken beliefs about scientific uncertainty and how some critics have argued that the most basic claims made by climate scientists are undermined. Here is their list of myths:
- "There is so much uncertainty and disagreement among climate models that they cannot be believed.
- The observed temperature increase is due to spurious data or faulty reconstructions of past temperature.
- Current global temperature is no warmer than the medieval warm period.
- Recent global warming is due to natural causes.
- Glacial transitions show that warming causes CO2 increase, not vice versa.
- Global warming has ceased in the last decade.
- The climate system is self-stabilising, and feedback mechanisms will counteract the effects of greenhouse gases."