Ed Berry’s latest denial of the cause of climate change (Feb. 5 Daily Inter Lake letter to editor) is another example of his factless claims and disinformation about this issue.

Multiple, independent lines of scientific evidence show conclusively that contemporary global warming is largely due to the human-caused increase in greenhouse gases, especially CO2, in the atmosphere. It’s not explained by any known natural drivers of climate change or by any natural cycles of long-term climate variability. So Berry’s claims that CO2 is not a pollutant and that “nature, not our CO2, drives climate” are patently false because emissions of this gas from human activities are the cause of ocean acidification and a major contributing cause of climate change.

The warming effect of CO2 and other heat-trapping gases is a well-established scientific fact and has been demonstrated with simple science experiments and satellite observations. It is also well established that changes in the amount of greenhouse gases in the atmosphere cause climate change. While many natural forces can also cause changes in the Earth’s climate — including variation in the planet’s path around (and tilt toward) the sun, variation in the sun’s energy output, volcanic eruptions, shifting ocean currents, and natural changes in CO2 and other greenhouse gases — the effect of these and other natural factors are now being overwhelmed by decades of greenhouse gas emissions generated from human activities, especially the burning of fossil fuels. They are now the major force driving the direction of climate change.

But Berry denies this reality. Instead, he willfully ignores the findings of many studies, which conclusively show that the combined effects of natural drivers of climate do not explain the global temperature increase observed over the past half century.

Over 200 scientific organizations worldwide hold the position that climate change has been caused by human actions and have issued public statements endorsing this position. It is also held by the national academy of sciences in more than 80 different countries, including the U.S. This widespread agreement is documented not just by a single study, but by a converging stream of evidence over the past two decades from content analyses of peer-reviewed studies, surveys of scientists, and public statements issued by virtually every membership organization of climate experts worldwide.

In a 2011 report requested by Congress, the U.S. National Academy of Science, America’s highest scientific body, affirmed as settled facts that Earth’s climate is warming and humans are causing it. It also concluded that the likelihood of those conclusions being wrong is vanishingly small because they have been so thoroughly examined and tested and supported by so many independent observations and results. It also concluded that human-caused climate change poses significant risks for a broad range of human and natural systems.

What’s more, a joint 2014 report from the National Academy of Science and the British Royal Society concluded that further climate change is inevitable due to the greenhouse gases humans have already emitted to the atmosphere. Moreover, the projected rate of global average temperature increase for this century due to the emission of greenhouse gases is greater than that of any extended global warming period over the past 65 million years.

Responding effectively to the challenge of climate change requires a full understanding by the public that there is a high degree of agreement among climate scientists about the fact that climate change is happening now because of human activities, and that the risks — including the possibility of abrupt and disruptive changes — will increase the longer greenhouse gas emissions continue unabated.

As someone claiming to have expertise in meteorology and holding up his Ph.D. in atmospheric physics as evidence of this expertise, Berry’s denial of this widespread agreement among climate experts and his continuing attempts to disseminate misinformation while ignoring well-established scientific knowledge about this is scientifically irresponsible. It clearly shows that he places his ideologically driven beliefs above well-established scientific evidence and facts, raising serious doubt about his intellectual honesty, objectivity, and credibility as a scientist.

Jerry W. Elwood, of Kalispell, is a retired director of the Climate Change Research Division of the U.S. Department of Energy. J. W. Thiessen, of Lakeside, is a retired former director of the Office of Health and Environmental Research in the U.S. Department of Energy.