A new report published today by the Center for the Study of Carbon Dioxide and Global Change challenges NASA scientist James Hansen's claims of a dire global warming future. In the report, physicist Sherwood Idso and agronomist Craig Idso conducted a comprehensive evaluation of Hansen's April 26, 2007 testimony before the House Select Committee of Energy Independence and Global Warming and concluded there is "very little evidence to justify [Hansen's] policy prescriptions for dealing with what he calls a 'dangerous climate change.'"

Considered by many to be perhaps the world's foremost authority on the 'greenhouse effect' of anthropogenic CO2 emissions, Hansen's statements are typically regarded as expressions of fact. "In many cases, however, they are merely his opinions," said Dr. Sherwood Idso, lead author of the report. "When Hansen's testimony is compared with what has been revealed by the scientific investigations of a diverse assemblage of highly competent researchers in a wide variety of academic disciplines, we find that he paints a very different picture of the role of anthropogenic CO2 emissions in shaping the future fortunes of man and nature alike than what is suggested by that larger body of work."

Among the inconsistencies between Hansen's House of Representatives' testimony and the scientific literature is Hansen's claim of a sea level rise this century measured in meters, due to "the likely demise of the West Antarctic ice sheet." However, the most recent and comprehensive review of potential sea level rise due to contributions from the wastage of both the Antarctic and Greenland ice sheets suggests a century-long rise measured in millimeters. Similarly, whereas Hansen claims the rate of sea level rise is accelerating, century-scale data indicate the mean rate-of-rise of the global ocean has either not accelerated at all or has actually slowed over the latter part of the past century.

Another Hansen claim that is at odds with reality is that atmospheric greenhouse gas concentrations are "skyrocketing," which is not universally true. The most important contrary example is methane, which has historically provided a climate forcing equal to approximately half that provided by CO2, but whose atmospheric concentration actually stabilized several years ago and has not risen since by any appreciable amount.

Also contrary to what Hansen claims is the fact that the earth is not any warmer now - and is possibly a fair amount cooler - than it was many times in the past. These warmer-than-present periods include much of the Medieval Warm Period of a thousand years ago, most of the Climatic Optimum that held sway during the central portion of the current interglacial, and significant portions of all four of the prior interglacials, when (in all six cases) the air's CO2 concentration was much lower than it is today. These facts are extremely important because they demonstrate that today's temperatures are not in any way unusual, unnatural or unprecedented, contrary to what Hansen claims.

Hansen also foresees a warming-induced "extermination of a large fraction of plant and animal species," with many at high latitudes and altitudes being "pushed off the planet." However, as demonstrated by the scientific studies cited in the Center's critique of Hansen's testimony, warming - especially when accompanied by an increase in the atmosphere's CO2 concentration - typically results in an expansion of the ranges of terrestrial plants and animals, leading to increases in biodiversity almost everywhere on the planet. Likewise, where Hansen sees nothing but "destruction of coral reefs and other ocean life" in response to a predicted CO2-induced acidification of the world's oceans, real-world observations suggest just the opposite.

Read the entire report (pdf) at: HansenTestimonyCritique.pdf

To read the report in html format, go here: hansencritique.