Inside Story

Climate science: dealing with the (minor) errors

Regardless of claims by polluters and sceptics, the IPCC’s science is overwhelmingly sound, writes Melanie Fitzpatrick from the Union of Concerned Scientists in Washington

Melanie Fitzpatrick 8 March 2010 1949 words

John Kerry, one of the authors of a climate change bill to be presented to the US Senate shortly. Center for American Progress

OVER THE PAST few months, the Intergovernmental Panel on Climate Change has been attacked for minor errors in its landmark 2007 report on climate change. These attacks have underpinned an intensified campaign against the IPCC across the western world. Here in the United States legislators and state attorneys-general are trying to use these flaws to thwart the Obama administration’s attempts to introduce policies to reduce emissions.

The IPCC has said it will review its process for creating reports in light of the few errors that have been found. If carried out with rigour, transparency and independence, such a review will confirm and strengthen the IPCC’s commitment to robust scientific assessment, and restore public confidence that has been shaken by an aggressive campaign to sow confusion about climate science.

Along with the manufactured controversy over stolen emails – driven by ideologues and anti-science bloggers who would rather attack scientists personally than grapple with substantive science – the recent attacks on the IPCC have given people already opposed to action yet another excuse to ignore the science. Those who choose to mischaracterise the scientific evidence about global warming are attempting to confuse the public and distract policymakers from addressing this issue. No matter how strong the science is, these well-funded contrarians would continue to oppose any policies that would make the oil and coal industries deviate from business as usual.

Overall, the IPCC’s conclusions remain indisputable. Climate change is happening now and human activity is causing it. Nations around the world will need to adapt to unavoidable climate impacts, including sea-level rise, changes in precipitation, disruptions to agriculture and species extinctions. But if we reduce our emissions dramatically, we can still prevent the worst effects of climate change.

THE IPCC is the world’s leading body for assessing climate science. At the centre of the debate is the IPCC, the world’s leading body for assessing climate science. Established in 1988 by the World Meteorological Organization and the United Nations Environment Programme, it is the organisation through which climate experts from around the world synthesise the most recent climate science findings every five to seven years and present their report to the world’s political leaders. The panel’s first report in 1990 spurred governments to create the United Nations Framework Convention on Climate Change, which remains the main body for climate negotiations.

The IPCC’s 2007 report is the most comprehensive synthesis of climate change science to date. Experts from more than 130 countries working over six years contributed to the assessment. More than 450 lead authors received input from more than 800 contributing authors, and an additional 2500 experts reviewed the draft documents.

The inclusive and transparent process by which IPCC assessments are developed, reviewed and accepted by experts and governments helps ensure the scientific credibility officials need when they formulate climate policies. As with any human endeavour – and especially given the size and coverage of the IPCC reports – errors are possible. They do not undermine the overall conclusions, which are subject to an exhaustive review process. It is a testament to the quality of the IPCC that errors have been few and, when identified, that they have been corrected. A concerted effort to improve the quality of the IPCC process is welcome but does not imply any serious deficiency in the content of the group’s 2007 report.

Instead of exposing the scandal of unfounded attacks on scientists and highlighting how minor mistakes in the IPCC report have been outrageously exaggerated, the mainstream media has largely aided attacks on highly respected and competent climate scientists. That’s unfortunate. When it comes to science reporting, journalists should emphasise what scientists do know and fulfil their mission to educate the public. Scientists don’t deserve the same treatment journalists reserve for he said/she said reporting on political issues. And framing scientific issues as conflicts rarely enhances public understanding of science.

Let’s consider the actual claims against the IPCC in detail. Most have been directed at the second volume of the 2007 IPCC report, “Impacts, Adaptation and Vulnerability.”

The Himalayan glaciers: Chapter 10 of this volume includes a statement that the likelihood that Himalayan glaciers will disappear “by the year 2035 and perhaps sooner is very high.” It is not clear how this unsupported assertion made it into the report, as it was openly challenged by some researchers during the review and editing process.

The claim is part of the full review of climate science and impacts provided in the dense, 3000-page report, but is not mentioned in its highly visible summaries for policymakers – presumably because the panel did not consider the claim to be reliable enough for its policymaker summary. The statement in the summary is much less specific. “If current warming rates are maintained,” it states, “Himalayan glaciers could decay at very rapid rates.”

What should not get lost is the fact that glaciers around the world are melting rapidly. A 2005 global survey of 442 glaciers from the World Glacier Monitoring Service found that only twenty-six were advancing, eighteen were stationary, and 398 were retreating. Overall, about 90 per cent of the glaciers scientists have measured are shrinking as the planet warms.

Glaciers are an important water supply for many people. And new analyses indicate that the shrinking land-based ice could contribute to a sea-level rise of 80 cm by the end of the century; although two metres is less likely, it is still physically possible.

The Amazonian rainforests: A sentence in chapter 13 of the second volume states: “Up to 40 per cent of the Amazonian forests could react drastically to even a slight reduction in precipitation; this means that the tropical vegetation, hydrology and climate system in South America could change very rapidly to another steady state, not necessarily producing gradual changes between the current and the future situation.”

In other words, global warming may be putting the Amazon basin at risk of more frequent and severe droughts. In drought years, trees are more likely to die and forests become more susceptible to fires. In wet years, fires often stop at the forests’ edge because the forest soil is so moist.

In this case, the science is right, but the passage gets its citations wrong. It refers to a report from the World Wildlife Fund and the International Union for Conservation of Nature (a body that includes more than 1000 government and non-government organisations and nearly 11,000 volunteer scientists in more than 160 countries). But the 40 per cent figure is from a different source: peer-reviewed papers written by Dan Nepstad, a senior scientist at the Woods Hole Research Center on Cape Cod, and his colleagues. A simple change in citation would very effectively have short-circuited this criticism of the report.

Nepstad and other researchers confirmed the link between drought and fire in papers published after the IPCC’s deadline for research that could be included in this section of the 2007 report.

Hurricanes: The 2007 IPCC report is also clear about how climate change would affect hurricanes. It concludes that hurricane intensity worldwide is likely to increase, and that there could be fewer weak hurricanes. The science linking climate change to increased severity of extreme weather is well-substantiated in peer-reviewed literature.

Even so, some contrarians have recently cited another, older controversy to try to give the false impression that these findings are in question. That controversy centres on how the 2007 report characterises the economic cost of an increase in severe weather. Contrarians point to a complaint by Roger Pielke Jr., a University of Colorado environmental studies professor, that the report misrepresents the reasons why economic losses from natural disasters have significantly increased over the years. Pielke says that the primary drivers for increased costs are economic factors, such as changes in wealth and population along the coasts.

The IPCC report does not dispute that fact, and it prominently cites Pielke’s research. Chapter 7 of the second volume also refers to one study that suggests that factors other than economic ones may be driving costs, but includes a number of caveats in that citation. This is in keeping with the IPCC’s task of presenting a balanced view of the literature. Specifically, the report concludes in its “Summary for Policy Makers”: “Costs and benefits of climate change for industry, settlement [cities and towns] and society will vary widely by location and scale. In the aggregate, however, net effects will tend to be more negative the larger the change in climate.” And it found: “Where extreme weather events become more intense and/or more frequent, the economic and social costs of those events will increase, and these increases will be substantial in the areas most directly affected.”

Pielke specifically objected to the fact that the IPCC includes unpublished material on the economic costs of natural disasters in its 2007 report. But this practice is not unusual for the IPCC. The panel’s procedures state that “it is increasingly apparent that materials relevant to IPCC reports, in particular, information about the experience and practice of the private sector in mitigation and adaptation activities, are found in sources that have not been published or peer-reviewed (e.g., industry journals, internal organisational publications, non-peer reviewed reports or working papers of research institutions, proceedings of workshops, etc).” The IPCC provides guidelines for the inclusion of such research, including clear citation. In any case, more published research is needed on the economic costs of climate change.

The urban heat island effect: Climate contrarians are falsely claiming that Eastern Chinese temperature data first published in a 1990 Nature paper is compromised by the “urban heat island” effect. The term refers to the fact that buildings and asphalt are darker than surrounding countryside, often making cities and population centres hotter. Scientists have studied this effect since the mid-1800s and it is extensively referenced in the scientific literature. Overall, climate science indicates that the urban heat island effect has no bearing on global temperature trends and is insignificant compared to other adjustments routinely made to make temperature records more accurate.

When scientists measure global warming, they examine how much temperatures have changed over time. For instance, an urban station may have warmer thermometer readings compared with a rural station in the region, but global warming will cause temperatures to rise at both stations. To determine trends, scientists compare the difference between the temperatures at stations today and their average temperatures in the past.

Scientists worldwide, including those at leading American institutions, routinely correct station data for changes such as shifts in station location, different elevation, different time of daily observation, different latitudes, and instrument changes over time. For example, after such adjustments for stations across the United States, there was no detectable difference between urban and rural stations comparisons in each region.

The 1990 Nature paper has since been backed up by other studies. And Eastern China, meanwhile, is warming in a way that is consistent with the rise in global average temperatures.

Global warming is here and it’s real. No amount of cherry-picking from the IPCC report will change that reality. Unfortunately, polluting industries and their allies are desperate to attack the IPCC and climate scientists generally. But that is only because they are losing. Here in the United States the public still supports comprehensive climate policy and an climate treaty. President Obama is prioritising administrative action on climate change. And US senators will soon unveil their proposal for dealing with global warming.

We are still moving forward on climate change, even as polluting industries and their allies try to drag us backward. •