Science thrives on debate. Only by challenging scientific findings do we expose weak arguments and substantiate strong ones. But the process relies on the debate being devoid of political taint and grounded in sound scientific knowledge. Sadly, that has not been the case in the recent barrage of criticism leveled against climate science.
The readers of Yale Environment 360 are by now familiar with recent questioning by some of the validity of the widely accepted science of climate change. The release of emails stolen from the University of East Anglia was used just prior to the Copenhagen Climate Summit to project an unflattering portrayal of climate scientists in general and to voice allegations that climate science was deeply flawed. (It is significant that the U.K. House of Commons Science and Technology Committee last month issued a report essentially exonerating the researchers involved of any ill intent or wrongdoing, as did an independent panel established by the university.) This episode was followed by accusations that the Intergovernmental Panel on Climate Change (IPCC), which I chair, had exaggerated the severity of climate change.
To call climate science a ‘hoax’ amounts to a tremendous disservice to science and to humanity.
Though some of the criticism has been thoughtful and was welcomed by the IPCC, much of it relied on unsubstantiated conspiracy theories and gross mischaracterizations that would be laughable were they not intended to create a bias in public perceptions on this critical issue. Certainly, in any human endeavor there is always room for improvement, and that is particularly true of enhancing the level of thoroughness in searching for new knowledge. In this context, the IPCC has listened and learned from the more reasoned criticism voiced recently. As I will explain later in this article, the panel is also taking action to refine its procedures in response to fair and objective criticism. But to call climate science a “hoax,” as some fringe critics have done, amounts to a tremendous disservice to science and to humanity as a whole.
Preparing Assessment Reports
Before responding to the criticism about the IPCC, I believe it is important to describe how the panel functions. Only by understanding how the IPCC prepares its reports can one put recent developments into perspective.
The IPCC’s primary work entails collecting and assessing published material on climate science and assembling it into Assessment Reports (ARs) that are issued every five to six years. These reports provide assessments on scientific, technical, and socio-economic factors, which can provide the basis for making rational policy decisions. The IPCC makes no policy recommendations of its own.
All the scientists who work on IPCC assessments devote their time voluntarily and receive no compensation. Yet their work is unprecedented in scale; it is the world’s most comprehensive source of climate change information. The latest assessment, AR4, completed in 2007, had more than 450 lead authors who worked during the course of several years to complete the report; their efforts were supplemented by about 800 contributing authors and some 2,500 expert reviewers.
At each successive stage of drafting, the report was carefully reviewed. A total of about 90,000 comments were produced during the review process. The authors considered and reacted to each of those comments. By the time it was completed, AR4 cited approximately 18,000 peer-reviewed publications. It also included a limited amount of gray (or non-peer-reviewed) literature in cases where peer-reviewed literature was unavailable. (For example, there is often no peer-reviewed literature on impacts of climate change, both current and projected, in many developing countries.)
The IPCC has a duty to correct or clarify any errors that may slip into reports of this magnitude.
AR4 has been criticized for exaggerating the severity of climate change. On the other hand, many regard the report as too conservative and an understatement of the impacts of climate change. This is due in part to the fact that preparing an assessment report takes several years. For instance, AR4 was based on scientific studies completed before January 2006, and did not include later studies that may show accelerated melting of the Greenland ice sheet and indications that sea levels may rise even higher than previously projected. These and other published material will be assessed in the AR5, which is scheduled to be completed in 2014.
With the enormous increase in published literature on various aspects of climate change, the lode of knowledge that the authors of AR5 will have to unearth will increase substantially, making the task ahead even more daunting. There is now much higher awareness worldwide of the scientific realities of climate change. There is also a much higher expectation of infallibility in all that the IPCC does, particularly since the panel received the Nobel Peace Prize in 2007.
IPCC procedures are robust and rigorous, but they can always be improved. Upholding exacting standards is a responsibility and a sacred trust that IPCC authors — and I — accept with the utmost respect and sincerity. It is our duty to correct or clarify the inevitable oversights and errors that may slip into reports of this magnitude and complexity.
With this in mind, I would like to provide a response to some issues that have given rise to recent controversy.
AR4 stated that the Himalayan glaciers could melt by 2035. This figure was incorrect and unfortunately based on a single unsubstantiated source. When this error came to light, the IPCC expressed its regret and noted it on its website. The error was contained in a single sentence and in one graphic representation out of AR4’s nearly 3,000 pages.
It did not appear in any of the IPCC summaries relied on by policymakers. In those summaries, the language states: “Glacier melt in the Himalayas is projected to increase flooding, and rock avalanches from destabilized slopes, and to affect water resources within the next two to three decades. This will be followed by decreased river flows as the glaciers recede.” This statement remains valid, as does the fact that widespread loss of glacial mass and reduction in snow cover will accelerate throughout the 21st century largely as a result of human activities that are warming our Earth’s atmosphere.
The IPCC was accused of exaggerating the extent to which the Amazon rainforest could be damaged by a decrease in rainfall. The paragraph in question correctly stated: “By mid-century, increases in temperature and associated decreases in soil water are projected to lead to gradual replacement of tropical forest by savanna in eastern Amazonia. Semi-arid vegetation will tend to be replaced by arid-land vegetation.”
This was a classic case in which controversy was initiated not by scientists but by the media.
This was a classic case in which the controversy was initiated not by scientists but by the mainstream media, which badly distorted the facts. Blogs and other articles argued incorrectly that a report, the “Global Review of Forest Fires,” should not have been cited as a reference, because it was published by two non-governmental organizations. But the paragraph in question accurately presented results in the literature it cited. It was a small part of a long, well-referenced discussion of Amazonian risk. Although the “Global Review of Forest Fires” was not a peer-reviewed document, it nevertheless was an important compilation, assembling information from more than 100 sources, including peer-reviewed scientific papers and reports from governments and non-governmental organizations, as well as news articles.
On March 18, 18 respected rainforest scientists from Brazil, the U.S., and the U.K. issued a lengthy statement reaffirming the IPCC’s conclusion that up to 40 percent of the Amazon rainforest is at risk because of climate change. Their statement can found online.
Another alleged exaggeration of AR4 was that climate change could reduce crop yields in parts of Africa by up to 50 percent. The only concern here was that in condensing the material from the underlying Working Group II Summary for Policymakers for the Synthesis Reports, the important qualifying phrase “by climate variability and change” was omitted from a statement that read: “Agricultural production, including access to food, in many African countries is projected to be severely compromised.” This is no way diminished or altered the scientific basis or the policy relevance of the statement included in the synthesis report.
Many of the IPCC’s conclusions about impacts in various regions of the world include the effect of climate variability, not just the effect of climate change. In the full underlying reports, this caveat was fully explained. This is another area where a small issue of the wording of one sentence — on a subject that was dealt with in a balanced way throughout the report — has been blown out of proportion.
Major findings of the AR4
None of these issues diminish in any way the major findings of the AR4, which presented voluminous, well-documented evidence of the steady warming of the planet. For instance, 11 of the last 12 years covered in the report (1995-2006) were found to rank among the 12 warmest years in the instrumental record of global surface temperature since 1850. The 100-year linear temperature increase for the period 1906-2005 was 0.74 degrees C. The temperature increase was found to be widespread around the globe and greater at higher northern latitudes. For instance, the Arctic region has been warming at twice the rate of the global average. The AR4 also documented the steady disappearance of Arctic sea ice, the retreat of glaciers worldwide, and changes in the timing of seasons around the globe — all convincing evidence of a warming world.
In addition, the report found that sea level increases were consistent with warming, having risen since 1961 at an average rate of 1.8 millimeters per year and since 1993 at 3.1 millimeters per year, due to contribution from thermal expansion of the oceans, and melting glaciers and ice sheets.
None of these issues diminish the major findings, which presented voluminous evidence of warming.
As for the projected impacts of climate change, several findings are of significance to policymakers. Based on current knowledge and trends, approximately 20 to 30 percent of plant and animal species assessed so far are likely to be at increased risk of extinction if increases in global average temperatures exceed 1.5 to 2.5 degrees C. At lower latitudes, especially in seasonally dry and tropical regions, crop productivity is projected to decrease with even small levels of temperature increase (1-2 degrees C), which would increase the risk of hunger. At the same time, coastal areas are projected to be exposed to increasing risks, including coastal erosion due to climate change and sea level rise. This effect will be exacerbated by human-induced pressure on coastal areas.
The health status of millions of people is projected to be affected, for example, through increases in malnutrition, diseases, and injury due to extreme weather events. It is reasonable to project increased frequency of cardio-respiratory disease due to high concentrations of ground level ozone in urban areas related to climate change. Infectious diseases will likely spread as the climate warms. The availability of water would also be impacted significantly by climate change, with exacerbation of current stresses on water resources.
Many adverse impacts can be reduced, delayed, or avoided by mitigation, and mitigation measures and investments over the next two to three decades will help stabilize levels of greenhouse gases in the atmosphere. The AR4 has determined that the cost of stringent mitigation is actually quite modest and is not likely to exceed 3 percent of global GDP in 2030, if the world targets a path of emissions that would stabilize global temperatures at a rise of between 2.0-2.4 degrees C. Mitigation measures also carry benefits such as higher energy security, lower levels of air pollution, and job creation.
The IPCC’s findings about already-observed changes, projections for the future, and mitigation options provide a robust framework for decision making.
The Road Ahead
I stand firmly behind the principle that the IPCC must do all that is humanly possible to eliminate errors or any statements that might be easily misinterpreted. It is for this reason that the IPCC, in tandem with the Secretary General of the United Nations, has requested the Inter-Academy Council to carry out a review of IPCC procedures and practices so that the work of the panel meets the highest possible standards and its assessments maintain a high level of credibility and reliability. The review will include the IPCC’s use of gray literature.
The public is entitled to demand clear and credible knowledge on which decisions can be based.
The scientific community, as embodied in the work of the IPCC, is ready to meet in all respects the increasing and exacting expectations of policymakers and the public. Given the importance and the serious implications of any actions related to climate change, the public and political leaders are entitled to demand clear and credible knowledge on which decisions can be based.
In a field such as this, perfect certainty about the future will remain elusive. But we have adequate certainty today based on the findings of the AR4, which give us a rationale for taking action and meeting the challenge of climate change. What actions are in the best interests of society should be the subject of a spirited, intense, and science-based global debate.
I sincerely believe that this period, difficult though it has been, will have a positive outcome. Climate science will be the better for it. The public will be better informed by it. And the scientific community will learn that it has to interact with and be accountable to the public.
We are living in an information age when any comments or criticism warrant an instant explanation or response. The IPCC has to develop the capability to do this. Gone are the days when an important subject like climate change could remain the preserve of ivory tower scientific institutions. Knowledge in this field is of critical relevance to society and will become increasingly so.
Though the controversy — and the misinformation surrounding it — may appear to have weakened support for climate science, I believe this will be short lived. With controversy comes discussion, and with discussion comes understanding. History is replete with examples of how politics temporarily trumped science, but the truth eventually triumphed.
Let’s hope it wins out in time for world leaders to take action.
Stuti Sharma, a research associate at The Energy and Resources Institute, contributed research for this article.