In the wake of punishing heat waves, historic droughts, extensive flooding and extraordinary melt activity on Greenland, many are asking if we are seeing long-predicted results of climate change, caused primarily by man-made heat-trapping greenhouse gas emissions. Recent studies on extreme events found in an Intergovernmental Panel on Climate Change (IPCC) report and the Bulletin of the American Meteorological Society suggest that such events may not be attributable to weather variability alone. They also echo warnings issued by scientists for decades.
A recent opinion editorial in USA Today argues against linkages between extreme weather and climate change. Further, the editorial disparages an overwhelming body of peer-reviewed science confirming climate warming and other changes.
We agree that climate attribution studies are still in their infancy and should be used with caution, but the scientific evidence is revealing the puzzle picture even as pieces are missing.
The recent IPCC report on extreme events and other peer-reviewed science present compelling evidence that the magnitude of heat waves, extreme coastal water levels, extreme precipitation events, and drought have increasing links to human-caused climate change. The scientific literature is less clear on linkages to hurricanes and tornadic activity.
The Guardian recently asked active climate experts about possible linkages between weather and climate change and an emerging thread is seen in their responses. Many have previously noted the baseball-steroid analogy and for good reasons. During the steroid era, there were more and longer home runs, although any given home run could not be conclusively linked to steroids. However, the inflated homerun statistics helped to clarify the link. Excessive heat-trapping gases are steroids in the climate system.
There are several issues with the USA Today opinion piece that must be addressed.
Peer review: Opinions are often put forth on climate change related topics. It is important that readers have a litmus test for credibility. We offer the following questions: Has the person published in the peer-reviewed literature on the topic? Is the person currently engaged in active research or objectively vetted analysis? Is the argument based on published findings in the peer-reviewed literature?
The peer-review process is important because it provides an objective manner for science and methodologies to be vetted. It ensures that mere conjecture is not “clouding” the issue. In some respects, it is analogous to the Food and Drug Administration (FDA) approval process, which prevents dangerous foods and medicines from reaching consumers.
The question of warming: All global temperature records, including the recently publicized Berkeley Earth Surface Temperature study (designed specifically to address concerns with other temperature studies and still to be subjected to peer review), show warming over the last century.
In the U.S., NOAA has continually reported heat record after heat record in recent years, including the warmest 12-month period on record in 2011-2012. Additionally, the number of record high temperatures is far outpacing record low temperatures in the US.
The “State of the Climate 2011” report, produced by the National Oceanic and Atmospheric Administration (NOAA) and its partners and published by AMS, is an excellent source for trends in current climate indicators.
Further, recent arguments noting stability in the temperature record are simply false. The temperature record is far from stable with changes that occur both from month to month and from year to year. No serious climate scientist would say that every year will be warmer than previous years when other influences, such as the oceanic currents, El Nino, or massive volcanic eruptions like Mount Pinatubo, can exert large but short lived influences on the global climate. Averages over recent decades show the steady increase in global temperatures. Consider the stock market: one does not responsibly draw conclusions about long-term trends from one year or even a few years’ fluctuations.
The carbon dioxide argument: The USA Today opinion editorial challenges the notion that greenhouse gases exert more of an influence on climate than the oceans. According to NOAA, without greenhouse gases in the atmosphere, including CO2, methane and water vapor, the average temperature of the Earth would be about zero degrees F instead of its present 57°F. There is no doubt that oceans have immense heat reserves and are one reason that Earth is not already warmer. The oceans have likely been absorbing much of the excess energy that might otherwise have gone into the atmosphere.
The argument that the small concentration of CO2 in the atmosphere cannot possibly be driving the temperature increases ignores well-established atmospheric physics theory dating back to Callendar (1938) and earlier. Building on this point, Climate Communication’s Susan Hassol and noted science writer/physicist Dr. Fred Bortz, fredbortz.com, independently made the point that tiny amounts of CO2 in the atmosphere make life on Earth possible.
The Sun: Careful measurements of the amount of the Sun’s energy reaching the Earth have demonstrated that there has been no increase in the last half century. During that time, global temperatures have increased strongly. Numerous studies have concluded that only human-caused increases in heat-trapping gases can explain the warming of the past half-century.
The Arctic: The following statement in the USA Today opinion piece is particularly troubling: “IPCC incorrectly predicted Arctic sea ice would disappear by now.” Not only is this false, it glosses over the fact that summer Arctic sea ice is in serious decline.
Summer ice loss this year is on track to match the record low reached in 2007. Even more alarming is the loss of multi-year ice. A good source of information on Arctic and Antarctic sea ice is the National Snow and Ice Data Center. One of the authors (Shepherd) recently served on a National Academy of Science study commissioned by the U.S. Navy. The report highlights an array of concerns about the Arctic ice and climate change that affect national security.
The USA Today piece closes with the statement, “Perhaps when the Atlantic flips cold, we will be hearing Ice Age scares again as we did in the 1970s.” Once again, this is a red herring. While a number of popular magazines ran pieces speculating about cooling, a clear majority of scientific papers published in this period supported global warming. Further, passage of the Clean Air Acts and reduction of reflective, cooling pollutants served to accelerate warming after the 1970s.
In summary, a host of information on climate science is available, but readers should consider the sources carefully. We recommend sites that reflect the best convergence of peer reviewed science, active research, and resources (e.g. NOAA’s climate.gov, various NASA sites, the IPCC, etc.). Professional and scientific organizations like American Meteorological Society, American Geophysical Union, Association of American Geographers, and others also have clear, science-based statements that serve as objective information sources for the public, policymakers, and the scientific community.
* Dr. J. Marshall Shepherd, is director of the Atmospheric Sciences program at the University of Georgia and President-Elect, American Meteorological Society; John Trostel is director of the Severe Storms Research Center at the Georgia Tech Research Institute