To the Editor:

As a research scientist, I read the recent exchange of letters debating the relative strengths and weaknesses of the data concerning "human-caused" climate change with equal parts amusement and chagrin.

Amusement because it was so easy to see how each side cherry-picked the statistics which supported their argument while casually disregarding those which argued against. Chagrin because I've seen first hand how this type of "quasi-professional" exchange only serves to weaken the role of science in the public arena as people, including our elected leaders, incorrectly discount Science on the premise that scientists rarely, if ever, reach consensus on complex and controversial issues.

In regards to the specific question of what role humans have played in modern climate change, I've pasted below a short series of excerpts from the just released Intergovernmental Panel on Climate Change "Headline Statements from the Summary for Policy makers of the IPCC report on the physical science basis of climate change." The IPCC report has over 600 contributing authors and 50 external reviewers and represents the most comprehensive synthesis of climate science available. The full report and summary statements can be found at http://www.ipcc. ch/.

Key statements include: Warming of the climate system is unequivocal, and since the 1950s many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased. Each of the last three decades has been successively warmer at the Earth's surface than any preceding decade since 1850. Ocean warming dominates the increase in energy stored in the climate system, accounting for more than 90 percent of the energy accumulated between 1971 and 2010 (high confidence). . . . . The rate of sea level rise since the mid-19th century has been larger than the mean rate during the previous two millennia (high confidence). . . . . The atmospheric concentrations of carbon dioxide (CO2), methane, and nitrous oxide have increased to levels unprecedented in at least the last 800,000 years. CO2 concentrations have increased by 40 percent since pre-industrial times, primarily from fossil fuel emissions and secondarily from net land use change emissions. The ocean has absorbed about 30 percent of the emitted anthropogenic carbon dioxide, causing ocean acidification. . . . Human influence on the climate system is clear. This is evident from the increasing greenhouse gas concentrations in the atmosphere, positive radiative forcing, observed warming, and understanding of the climate system. . . . Human influence has been detected in warming of the atmosphere and the ocean, in changes in the global water cycle, in reductions in snow and ice, in global mean sea level rise, and in changes in some climate extremes. . . . It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century.

There's a difference between "not getting it" and "not liking it." Scientists can help with the former. The latter is opinion and you're welcome to it whatever it may be. However, there's never any excuse for willful ignorance.

Michael Cooperman

Manchester

Dr. Cooperman is an ecologist actively researching how climate change will affect freshwater fisheries yields of the developing nations of the tropics.