To the editor:

I have enjoyed reading Naturally Speaking by Steve Lekwa over the past several years. I’ve even used one of Steve’s articles (“Thermoregulation keeps creatures cool in hot weather”) in a class I teach at Iowa State University. When I read the July 20, 2017, edition titled “Warming, or just warm?” I felt compelled to write this letter to the editor. The topic of Steve’s latest installment is something with which I am familiar, and I would like to add my thoughts.

In the first paragraph of his column, Steve says “There’s a tremendous amount of science out there to suggest that warming is real, but even scientists aren’t completely in agreement, especially when trying to place the blame for the current rise in global temperatures on human causes.” Steve’s statement about scientists not being in agreement doesn’t personally bother me, because as a practicing scientist I am intimately familiar with how science works. However, this statement can confuse readers who are not as familiar with the scientific process.

Science is an interesting profession. Scientists seek the “truth” but are themselves human, and we all know that humans can’t be perfectly objective and therefore don’t always agree. We should never expect absolutely all scientists to be in agreement on any topic.

For example, there are scientists today who don’t support the theory of biological evolution, yet this is the only line–of–thought that has been able to explain the many changes in living organisms we observe on our planet, including why farmers, over time, have to make adjustments in how they manage weeds in their fields as they become resistant to specific herbicides. Could this scientific theory be wrong? Yes. But no alternative that can hold up to the scientific method has been discovered.

I have co–taught another course called “Introduction to Weather and Climate” at Iowa State for the past 13 years. In this class, we review reports written on the subject of climate change authored by an organization called the IPCC, the Intergovernmental Panel on Climate Change. The IPCC in reality is just a group of practicing climate scientists (including three of my colleagues at Iowa State) from all around the world who have been charged by the World Meteorological Organization and the United Nations to inform world leaders about the current state of knowledge concerning the climate system.

Do absolutely all scientists agree with the IPCC? No. But I see the IPCC as the best possible source of information on this topic. Five “Assessment Reports” have been issued since the IPCC was initiated in 1988, the last in 2013. You can find the latest “Summary for Policymakers” here: What does the IPCC say about climate change and it’s causes?

In terms of observed changes, the IPCC makes the following statement. “Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased.” My dictionary says that “unequivocal” means “leaving no doubt,” and that “unprecedented” means “never done or known before.”

And what is causing these changes? Imagine putting a big box around Earth. Energy from the sun in the form of solar radiation comes into the box. If the same amount of energy goes out of the box (the infrared radiation emitted by Earth), then the total amount of energy in the box stays the same and the global climate system is stable.

Right now less energy is going out of the box than what is coming in. Consequently, the Earth system is warming. What fraction of this imbalance is due to natural causes (changes in solar radiation, or energy coming into the box)? About 2 percent (and most likely somewhere between 0 and 9 percent). The rest is associated with human activity, the vast majority caused by the increase in greenhouse gases in our atmosphere.

There are several other statements in Steve’s column with which I wholeheartedly agree. These include the following. “I, personally, don’t like the term global warming, even if average temperatures around the world are getting warmer. I’d rather call it climate change.” Yes, climate is much more than just temperature. It is also wind, humidity and precipitation to name a few. These other aspects of climate are also changing, and could be more problematic for humans and other living organisms than temperature.

“Climate has never stopped changing, but usually changes at a rate that most life forms can adapt to… It’s the rate of change that should be of greatest concern.” Yes, it is the extreme rate of change that has been observed in the last several decades, and the rate of change expected in coming years, that distinguishes past changes with what we are experiencing now. This is a new type of hurdle for life on Earth.

Finally, Steve hits it right on the head when he says, “It’s going to be warm today, and downright hot into the week ahead. Is it global warming or climate change? It’s impossible to say on any given day.” Only over periods of time longer than a few decades can climate change be discerned. But it has been discerned, and humans are responsible for at least 90 percent (and perhaps all) of these changes. Not all scientists agree with this, and we should of course remain open to other explanations as science continues forward, but in the meantime, it’s foolish to ignore what the IPCC says is the best knowledge we have concerning Earth’s climate.

Brian Hornbuckle