by Jacob Haqq-Misra Friday, October 3, 2014
The latest report from the Intergovernmental Panel on Climate Change (IPCC), released piecemeal over the last year, reports “unequivocal” warming of the climate system due to increasing greenhouse gas concentrations, further emphasizing the need for global mitigation and adaptation schemes. But not everyone is ready to curtail carbon emissions, and the increasing clamor from skeptics and deniers — along with potential overstatements and even understatements by scientists — creates a polarized political environment that complicates efforts to communicate science effectively.
The major conclusions of the IPCC’s fifth assessment report (AR5) are not surprising: Temperature trends since the 1950s show an unprecedented rate of warming, and indicate that human influence — primarily through the release of greenhouse gases — is “extremely likely” to be the dominant cause of this change. These conclusions follow on those of the first four assessment reports; however, many people — primarily climate change skeptics, but also some scientists — have argued that the language in AR5 tends to minimize uncertainty and overstate confidence.
One of the biggest issues for critics of AR5 relates to the so-called “slowdown” in warming in recent years. The report’s executive summary describes this statistical observation with carefully chosen words: “Due to natural variability, trends based on short records are very sensitive to the beginning and end dates and do not in general reflect long-term climate trends. As one example, the rate of warming over the past 15 years (1998–2012; 0.05 degrees Celsius per decade), which begins with a strong El Niño, is smaller than the rate calculated since 1951 (1951–2012; 0.12 degrees Celsius per decade).” The AR5 authors indicate possible explanations for such variability, and many research groups have published analyses in attempts to explain this recent climatic episode.
Yet statements like these open the door to arguments that all of climate change can be explained by so-called “natural variability.” The fact that the AR5 report does not spend a great deal of time discussing this recent slowdown has also been pointed to by critics and media alike, who argue that the IPCC is politicizing its findings by emphasizing results that favor their predetermined conclusion while minimizing contrary evidence. Future research into decadal climate variability will yield a better understanding of the physics of climate, yet the present lack of knowledge gives critics reason to question the IPCC’s broader conclusions.
The IPCC authors must have known that this slowdown in warming would attract attention, and preemptive measures in the report that thoroughly discuss the data and uncertainties could have helped to establish a precedent of open communication. As it stands, the lack of direct attention to these uncertainties has caused some distrust for the rest of the report’s conclusions, which makes the communication of climate science all the more difficult. Individual scientists should bear a responsibility to ensure accurate communication, especially when uncertainties are involved, in order to maintain as objective an approach as possible.
The AR5 also focuses on the concept of “climate sensitivity,” which refers to the change in global temperature predicted to occur from a doubling of atmospheric carbon dioxide. Pinpointing a value of climate sensitivity has become somewhat of a holy grail for climate scientists, although the AR5 report illustrates just how difficult this quest has been. The “likely” range of climate sensitivity is reported to be in the range of 1.5 to 4.5 degrees Celsius. This is only a modest revision to the 2007 IPCC report (which gave a range of 2.0 to 4.5 degrees Celsius) and is exactly the same as the range given in the first IPCC report in 1990.
Whether this reflects the complexity of the climate system, the limitations of available data or simply the futility of trying to improve estimates of this number, many critics have pointed to this as evidence of a lack of progress in climate science. If no progress has been made in almost 15 years, so the argument goes, then why bother with the entire IPCC process in the first place? Metrics such as climate sensitivity are designed to aid in communication, but the lack of further constraints on climate sensitivity works to obfuscate actual progress in climate science. Scientists share part of the responsibility for this confusion by fixating on climate sensitivity rather than incorporating a broader range of predictors for future climate.
A major challenge to the accurate communication of AR5 arose with the release of two reports from a group of skeptics known as the NIPCC (Nongovernmental International Panel on Climate Change). Led by physicist Fred Singer, a long-time climate skeptic, the first report bears the conclusive title “Nature, Not Human Activity, Rules the Climate” and was published by the conservative think tank the Heartland Institute. Although dismissed by scientists as being largely propaganda, these NIPCC reports have influenced media discussions and public perceptions of climate change by masquerading as a consensus document from “world leading” experts that should be read at the same level as IPCC reports. Debunkers have had no difficulty in identifying fatal flaws in the logic of the NIPCC reports, which deny outright the primary conclusions of the AR5 report and reject from the start any notion that a carbon tax would help to curtail emissions. Honest skepticism in science should never be abandoned, but these NIPCC reports attempt to disguise a predetermined political agenda behind a façade of dishonest scientific skepticism.
The constant stream of misinformation and propaganda creates difficulties when scientists attempt to describe uncertainties about the climate system with the public, the media and policymakers. Uncertainty is inherent in science, but critics of climate change often highlight any one source of uncertainty to cast doubt on the entire process.
Addressing the problem of climate change requires political action today, but the scientific community should also take caution to avoid overstatements and understatements that can be interpreted by critics as attempts to conceal or mislead. As the IPCC strives to improve its internal processes, so too should all scientists strive for transparency and objectivity in communication.
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