Space Science and Engineering Center University of Wisconsin-Madison

As people around the world discuss climate change and its impacts, one group is busy at work, analyzing up-to-date scientific research in the hopes of creating a resource for assessing climate change. In fact, the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC) is on its way and will be released to the general public in 2014.

Hundreds of scientists and experts from all over the world are selected and contribute on a volunteer basis to the writing and review process of the IPCC reports. As one of the leading scientists in tropical cyclone research and climate trend analysis, Jim Kossin, a NOAA research scientist stationed at the Cooperative Institute for Meteorological Satellite Studies (CIMSS) at the University of Wisconsin-Madison, has been a lead and contributing author for five report chapters.

As his assessment work for the AR5 neared completion, Kossin shared his story of the IPCC, describing his four-year experience as “a little overwhelming but I very much enjoyed it and have learned a lot.” His story also lifts the veil of the IPCC assessment process–a process that often generates curiosity.

The IPCC is a Nobel Prize-winning, scientific intergovernmental organization formed for the assessment of climate change. It was established by the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP) in 1988 with a mission to provide, for policymakers and the general public, the most comprehensive and authoritative scientific assessment of the current knowledge in scientific, technical and socio-economic aspects of climate change.

The IPCC publishes assessment reports every five or six years to cover the most recent advances in climate science. To ensure the balance and inclusiveness of the assessment, the reports are based on peer-reviewed scientific literature written by leading scientists and experts representing both developing and developed countries in their areas of expertise. Given the highly competitive nature of the author selection process, being a lead or contributing author is regarded as an honor for scientists.

“Part of that [the reason for being selected] is I am lucky,” Kossin said while smiling. “I happen to work in a particular branch of the field that is of interest–this idea of tropical cyclones in a changing climate, not that many people do this kind of work,” he said.

Kossin’s research focuses on analyzing tropical cyclones (hurricanes) and their relationship to global climate change.  He uses the relationship between satellite data and hurricane metrics to estimate tropical cyclone intensity and to study surface wind structure.

Before his nomination to the IPCC, Kossin published a series of articles related to analyzing the hurricane record and climate trend studies. In 2006, he was invited by the United States Global Change Research Program (USGCRP, formerly the United States Climate Change Science Program (USCCSP)) to be a lead and contributing author of the Synthesis and Assessment Product 3.3 (SAP), an assessment report on weather and climate extremes in a changing climate focusing on North America, Hawaii, the Caribbean, and U.S. Pacific Islands.

Kossin said the SAP got him “involved in the idea of assessment and being lead author on them.” Later, he was nominated to the IPCC and officially appointed in September 2009 as a lead author of the Special Report on “Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation” (SREX), Chapter 3 “Changes in Climate Extremes and Their Impacts on the Natural Physical Environment.” Additionally, he became a contributing author to Chapter 9, “Case Studies.”

The IPCC report writing and assessment duties were distributed among three Working Groups (WGs). Kossin has been involved in Working Group I (WGI), a team composed of physical scientists tasked with assessing scientific aspects of the climate system and climate change. Working Group II (WG II) was comprised of social scientists who were to evaluate the vulnerability of socio-economic and natural systems to climate change, consequences and options for adaptations and mitigations. Working Group III assessed mitigation options for limiting greenhouse gas emissions.

In most cases, IPCC reports are split and composed independently by each working group based on their own expertise. But SREX was a joint effort between WG I and WG II. It assessed the scientific basis and the risk of human-induced climate change, the potential impacts on natural disasters, adaptation and mitigation options, as well as strategies to manage relevant risks. An ultimate goal of IPCC reports is to provide policymakers with a resource for climate-related decision-making and risk management.

In Chapters 3 and 9 of the SREX, Kossin’s participation focused on an assessment of three discrete areas–the scientific literature on observation and projection in changes of extreme weather and climate events, attribution and causes, and case studies. Specifically, Kossin and his co-authors contributed the section on tropical cyclones.

Kossin is also serving as a lead author on a chapter new to the AR 5. Titled “Climate Phenomena and their Relevance for Future Regional Climate Change” (Chapter 14), this chapter focuses on recent scientific research in regional climate change.

Regional climates result from the complex interplay between large-scale climate phenomena, such as tropical cyclones, monsoons, and the El Niño–Southern Oscillation (ENSO) and local physical processes. Large-scale climate phenomena are increasingly well-simulated and studied by global climate models, establishing a useful scientific basis for understanding and evaluating regional climate change.

Kossin explained the importance and usefulness of regional climate research by citing the example of ENSO.

“We are interested in behavior phenomena like ENSO: how it’s changing, and its relevance to certain regions. For example, Australia, depending on whether the ENSO oscillation is in the warm or the cold phase, they [Australia’s regional climates] go from drought to flooding. So, to that particular region, any change in the behavior of ENSO could be a very big deal.”

Specifically, Kossin evaluated studies of the impact of regional climate change on tropical cyclones and synthesized research findings that sought to demonstrate how regional climate change would respond to climate variability such as ENSO.

Participating in the IPCC assessment and review process is a long-term commitment. In addition to carefully considering all peer-reviewed scientific studies in related topic areas, the IPCC authors also need to determine how to compile these findings, especially the conflicting ones, in a meaningful way.

According to Kossin, reference lists always include hundreds of papers that need to be read thoroughly by each IPCC lead author. Yet reading all of the literature is not the most challenging part when compared to the literature synthesis process.

“The synthesis is important. Anyone can restate the main points of a whole lot of papers. We need to do a little bit more than that,” said Kossin. Assessment reports require authors to evaluate each paper carefully and relate each finding to relevant scientific information or to what people already know. The ultimate goal of all these efforts and of the summary itself is to make a statement of likelihood.

Kossin noted that it is crucial for IPCC authors to be careful, accurate and objective in the assessment process. They should present scientific findings and perspectives as inclusively as possible, objectively and without any agenda.

To illustrate, Kossin cited a case in his assessment process.

“There are almost an equal number of papers that say the recent changes in the climate of the North Atlantic region is dominated by natural variability and an equal number of papers saying that it is dominated by the behavior of pollution aerosol,” said Kossin.

The interesting part, and the challenge, is that all of these conflicting papers are based on high quality scientific research, many of which were published in high profile journals like Nature and written by well-known scientists. Their models appear equally sound, and their conclusions are well-grounded. Kossin said he had to accept this fact and present it as is. “You cannot say we don’t know, you would say we know quite a lot, but there are a lot of uncertainties in the final answer,” he noted.

In the process of composing the IPCC reports, authors follow writing guidelines, italicizing very specific words in the likelihood statements to indicate confidence level. As Kossin explained, from “Very Unlikely” to “Virtually Certain,” each word has a specific meaning associated with a numerical probability to define the level of certainty in each statement.

“To make a step from ‘likely’ to ‘very likely,’ you have to have a lot of new evidence,” Kossin said.

Once the first report draft is complete, it is disseminated for open public review. With a few restrictions, almost anyone can make comments on the draft, and all comments receive a response from the lead authors. Kossin said that in Chapter 14 alone, there were more than 1500 comments from the final open public review. Though it is laborious work, Kossin places a high value on the open review process—a great majority of the comments are helpful in improving the accuracy, objectivity and balance of the report’s content.

In 2010, “Climate Gate” and the Himalaya Glacier mistake in AR4 generated broad criticism about the IPCC. Some climate skeptics even discredited the evidence in AR4 and called IPCC scientists alarmists. Although these mistakes did not invalidate the other evidence and report conclusions, many critics pointed to problems in IPCC procedures needing reform.

Referencing these issues, Kossin agreed that because the IPCC operates mostly on a volunteer basis, this framework may create some challenges due to time limitations of the participants. He also suggested that he and his fellow IPCC authors need to always be careful and accurate in evidence-checking and balancing information.

To date, the draft of AR5 has been completed and submitted to governmental bodies for acceptance. Kossin values the experience of his four years’ work with the IPCC and noted that these assessment reports are “the best thing that we have got.”

Given the significant time commitment and intense effort involved with the IPCC assessment, taking on the role of lead author usually means that the scientists have to sacrifice their own research or personal time to read and assess other people’s work. Kossin was impressed by the significant number of scientists who volunteered to serve, and was honored to contribute in the most comprehensive and authoritative assessment report in climate science to date.

“We want to provide the truth as the literature suggests and we want to be able to assess things and provide a realistic, objective, uncolored evaluation of what we know and what we don’t know. It is not an opinion piece, it is an assessment,” Kossin concluded.

by Zhengzheng Zhang