Can’t extrapolate today’s weather

Are recent snow accumulations in the Cascades, and recent record low temperatures elsewhere, signs that global warming has abated? (Feb. 15 letter, “What snowpack decline in West?”) Is the fact that annual global mean temperatures trended downward for the eight-year period from 1978 to 1986, and the eight-year period from 1979 to 1987, a sign that global warming has abated? The answer to both questions is no. These comparisons take short-term weather variability and incorrectly assume it represents a long-term pattern.

Check out the chart in the Jan. 11 post, “Uncertainty, noise and the art of model-data comparisons” at www.realclimate.org

The chart and its follow up discussion explain why it’s flawed to extrapolate long-term trends from short-term weather variations. As the article points out, “… the climate system has enormous amounts of variability on day-to-day, month-to-month, year-to-year and decade-to-decade periods. Much of this variability is apparently chaotic and unrelated to any external factor — it is the weather.”

As for our climate system, today atmospheric CO2 concentrations are at an all-time high and still climbing. Over the past 500,000 years, concentrations have fluctuated between 200 and 300 parts per million (ppm) of CO2. These fluctuations took place over 100,000-year cycles — plenty of time for natural systems to adjust. Over the past 50 years, CO2 concentrations have increased by nearly 100 ppm to just under 400 ppm!

Climate change is a question of physics, not ideology. During past fluctuations, if a 100 ppm drop from 300 to 200 ppm in atmospheric CO2 saw the formation of mile-thick ice over much of North America, what does a 100 ppm increase from 300 ppm to 400 ppm mean for planet Earth? This is the more relevant question. Complaints about the weather are distractions.

Gary Lintz

Lynnwood