M.D. Harmon, in his April 27 column (“Changing their tune on global warming trend”), cites an apparent change of heart by James Lovelock and a letter to the administrator of NASA signed by 49 former NASA employees to support his view that “the idea that human action is causing climate change is becoming increasingly incredible to governments, astronauts, neutral scientists and ordinary taxpayers.”

However, the consensus of working scientists of human-induced climate change approaches 97 percent. Only two years ago, the National Academy of Sciences released three reports confirming the scientific consensus that the climate is indeed changing and that human activities are a major cause.

Although contrarians such as Harmon enjoy disparaging the Intergovernmental Panel on Climate Change, the IPCC’s periodic assessments represent the considered judgment of the world’s climate science community.

Since the first IPCC assessment in 1990, successive reports show a trend of growing certainties: first about the basic science; then about the human connection; and finally a growing alarm regarding the projected environmental and economic impacts of rapid climate change.

Since 2001, the IPCC’s conclusions have been supported by the national science academies of 32 separate countries.

Climate skepticism is well-funded. Paralyzing partisanship and denial do not belie the science. We could go on. Harmon’s two tales in no way prove his point, which simply flies in the face of reality. The science is sound.

The discussion today must be how people in Portland, in Maine and across the nation swiftly respond to the causes and effects of climate change in ways that support progress and economic health and avoid unnecessary costs.