By Judy Kroeker

Do you have a point you’d like to make or an issue you feel strongly about? Submit a letter to the editor or a guest column.

My daughter, Kristy J. Kroeker, is an assistant professor of ecology and evolutionary biology at the University of California, Santa Cruz. I sent her the guest column by Paul deWitt, entitled “The Problem with Climate Alarmism,” published on May 6, asking her to help me make sense of it. The following is her response to me:

Hi Mom,

Thanks for sending this along. It saddens me to see the distortion of the science in this article. There is some truth in many of the author’s bullet points, but all of the context is missing — which is what is confusing.

So, yes, the Earth’s history is long and there have been major climate cycles and changes in the past. The changes in temperature on geological timescales have been caused by the movement of the continents, which changes ocean circulation and is a major determinant of climate, and minor changes in our distance from the sun (called Milankovitch cycles) or sunspots. The Milankovitch cycles are predictable, and they are what cause the glacial and interglacial cycles in Earth’s history. All of these changes occur over very long geological timescales. Thus, the climate changes the author is referring to often occurred over hundreds of thousands to millions of years. These time frames allowed for the evolution of plants and animals to the changing climate. We know that plants and animals can exist in much warmer climates than they are now, but they need time to make the adjustments. In part, it is the rate of the current climate change that is the problem.

We have also had climate changes in Earth’s history associated with volcanic eruptions that release a bunch of CO2 into the atmosphere. These are slightly more comparable to current climate change. There is a huge body of research that is actually studying these spikes in CO2 and temperature to better understand the potential ecological consequences of the current climate change. What climate skeptics often fail to mention is that the periods of warming that are most comparable to the current situation are often associated with mass extinction events. We have had five mass extinction events in the history of our planet. I find it discouraging when people fail to understand that we have seen warming in the past, but from 40 to 96 percent of the species on the planet went extinct during the most comparable climate change events! That is what I mean when I say it is missing the context.

We actually have very good evidence for the link between CO2 and temperature. The statement the author makes about warming preceding CO2 comes from a paper a few years ago, where scientists showed that during a major warming event in the past, the CO2 concentrations increased a few hundred years after the initial warming. This is because the ability of the oceans to hold CO2 is dependent on the temperature —warm water can hold less CO2. In this particular event, temperature initially rose due to a Milankovitch cycle (changes in the sun’s distance). This caused the oceans to warm, which caused them to release CO2 that was previously dissolved and stored in the colder ocean into the atmosphere. Then, this CO2 exacerbated the warming initially caused by the change in the sun’s distance. If the actual science paper was more accessible to the general public, it would be clear that the authors of that study were never arguing that atmospheric CO2 concentrations aren’t linked to warming — they unequivocally are, according to 97 percent of scientists — but it is easy to pull the pieces out that create a storyline that the science is up in the air or refutable.

Love, Kristy

In my opinion, we, as a species, are contributing to increased CO2 in the atmosphere. How much — I don’t know — but to cherry pick facts to support a position is not helpful.

— Judy Kroeker lives in Sunriver.