Receding glacier climate change global warming

A receding glacier

I appreciate that Patricia Lamb (letter, June 7), and certainly others, are “conflicted” about climate change. She hears contradictory opinions on a complicated topic, from nominally authoritative figures. She correctly demands that scientific assessment be “comprehensive, objective, transparent and empirical.” Like me, she recognizes and deplores that opinions on this topic often reflect a “political mindset” more than objective analysis. Finally, she asks for “proof” that human-generated CO2 is the culprit in global warming.

Begin with the empirical part, the data, where Lamb knows good science begins. Two empirical facts are incontestable. First, CO2 in the atmosphere is increasing at an average rate consistent with the rate at which it is released by fossil fuel burning. (Actually, the oceans are absorbing some too, and yes, there is a strong seasonal variation associated with vegetation changes.) Second, average global temperatures are increasing, especially in the arctic. The four warmest years on record, according to NASA, have been the last four. Are these two facts causally related, as a consensus of climate scientists say, or are they just coincidental? That is the $10 trillion question Lamb wrestles with.

Lamb is not the first to voice the fear that the “consensus of climate scientists” is merely an example of “group-think,” that scientists are conformists unwilling to buck trends. But here she shows herself to be unfamiliar with the culture of science, where skepticism rules, where bad data are ultimately found out, where wrong hypotheses are abandoned. The scientific method and culture together make science missteps self-correcting, a key to human progress. Mavericks succeed in this culture, but only if they too follow Lamb’s charge to be comprehensive, objective, transparent and empirical. Screaming “Chinese hoax” is not good enough. I have looked for credible alternatives to the basic climate science narrative. There are none to be found, only variation of detail. Notwithstanding occasional bad actors, climate science has the overall objectivity and integrity that Lamb seeks.

The analyses that say increasing CO2 concentrations lead to a warmer planet are based on established science, but they are devilishly complex. How can we judge whether an opaque computer model’s worrisome climate projection is credible? This is the crux of Lamb’s plea for a “proof” that action is required.

At first glance the task seems impossible; indeed “proofs” are for mathematicians. But the scientific method (make an hypothesis, predict something, measure it, compare) allows anyone, not just specialists, to judge the models. We are all participating in the experiment right now. Computer models of 2000 included the presumed effects of human-generated CO2 on climate. They predicted higher 2018 temperatures. 2018 came and it was hot. The predictions were not perfect but good enough to be credible, not only in getting global averages but in predicting regional variations. Since 2000 got 2018 about right, would it be prudent to dismiss what today’s models say about 2036? Lamb, you be the judge.

Other predictions could be cited. Steve Running told us over a decade ago that the initial impact locally would be earlier dry forests. Was there not smoke in Missoula this May?

Verified hypotheses are not proofs, but science generally does not deal in proofs. Each year that CO2 and temperature trends continue to track together, a strong case gets stronger. It was strong enough in 2000 for Al Gore to make it a centerpiece of his presidential campaign. It is exponentially stronger now.

Surely the danger of inaction exceeds the danger of overreaction that Lamb fears. Surely the debate must be about how to respond, rather than whether to respond.

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David Andrews of Missoula is a retired physicist, former technology company executive and former University of Montana adjunct professor in physics.

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