Emails, Dr. Steven Quiring, associate professor, Department of Geography, Texas A&M University, May 8 and May 12, 2015
On 5/8/15 11:45 AM, Price, Asher (CMG-Austin) wrote:
I’m a reporter with the American-Statesman, the daily newspaper in Austin.
I’m writing because my editors have asked me to fact-check a statement
by Austin City Council member Don Zimmerman. Recently, during a
presentation by Katharine Hayhoe to the Austin City Council about
climate change, Zimmerman explained that he didn’t see any evidence of
a link between industrial emissions and warming. Here’s the statement
I’ve been asked to check: “You don’t have to be as smart as a
fifth-grader to know *what causes the climate is the Sun*. The Sun.
I have people tell me, ‘carbon dioxide warms the Earth.’ No, it
doesn’t. The Sun warms the Earth.”
Is the statement *“what causes the climate is the sun”* true? Half-true?
False? Misleadingly false?
If you could call (512-417-8200 is my cell) or write me back, I’d
FYI, here’s a short video that includes Zimmerman’s remarks.
This statement is misleading.
The sun is important. It is the primary source of energy for the climate system. However, the Earth's atmosphere is also very important. Compare the temperature of the moon and the Earth. Both are about the same distance from the sun, but the moon has an average surface temperature of about -5 degrees C (23 F) and the Earth has an average surface temperature of about 16 degrees C (61 F). Why is there such a large difference? If the sun was the only thing that mattered, both would have a similar average surface temperature. It turns out that having an atmosphere is very important. In particular, the Earth's atmosphere contains a number of greenhouse gases that are very effective at absorbing energy (at certain wavelengths) and re-radiating it back to the Earth's surface. The most important greenhouse gas is water vapor.
It is responsible for 2/3 of the greenhouse gas warming. Other greenhouses gases like carbon dioxide, methane, etc. contribute the remaining 1/3. The impact of greenhouses gases (like carbon dioxide and water vapor) is significant. If Mr. Zimmerman thinks that having an atmosphere does not matter, perhaps he should try to live on the moon for a while.
Of course there is lots more complexity. Average temperature is a poor measure of a planets temperature... so mean surface temperatures on the moon (at the lunar equator) can reach almost 117 degrees C (260.6 ºF) at noon and then drop to below -173 degrees C (-279.4 ºF) during the night.
So the Earth's atmosphere also moderates the temperatures and makes them less extreme.
In terms of greenhouse gases, water vapor is by far the most important greenhouse gas, but it is also the one that is least influenced by human activity. Global atmospheric water vapor concentrations are determined by the amount of energy available to evaporate water from the oceans (as well as wind speed and vapor pressure gradient). Carbon dioxide is one of the greenhouse gases that is most directly influenced by human activities (burning fossil fuels, etc.). It gets most of the attention, because it is the greenhouse gas that we can influence the most.
On 5/12/15 12:07 PM, Price, Asher (CMG-Austin) wrote:
Just a quick follow-up question. I bounced the same Zimmerman claim
off Katharine Hayhoe herself and she had a slightly different take,
one that hinged on a technical understanding of climate. (Below.)
Among the things she writes: "It's having an atmosphere that causes a climate to exist. If a planet doesn’t have an atmosphere, it does not have a climate."
(This is close to, but not quite, what you had written. Is that right
that a celestial body requires an atmosphere to have a climate?)
Staff Reporter, Austin American-Statesman @asherprice Tel. (512)
From: Katharine Hayhoe
Sent: Monday, May 11, 2015 6:16 PM
To: Price, Asher (CMG-Austin)
Cc: Laura James
Subject: Re: fact-check of zimmerman comment: "what causes the climate is the sun."
Hi Asher, thanks for your patience! I have been traveling this past week, so missed your original email.
Here’s the statement I’ve been asked to check: “You don’t have to be as smart as a fifth-grader to know what causes the climate is the Sun. The Sun. I have people tell me, ‘carbon dioxide warms the Earth.’ No, it doesn’t. The Sun warms the Earth.”
Is the statement “what causes the climate is the sun” true? Half-true? False? Misleadingly false?
As a scientist, I would say false to “what causes the climate is the sun” and half-true to “what causes the climate TO CHANGE is the sun”. I realize the second quote is not what he said, but I think that might have been what he meant, so I’ll address both of them.
STATEMENT: “what causes the climate is the sun”
EXPLANATION: Google defines climate as "the weather conditions prevailing in an area in general or over a long period.” The sun shines on Mercury and on the moon, just as it does on the Earth. However, Mercury and the moon do not have any weather conditions, nor any climate - because they do not have an atmosphere. So by this definition, the sun does NOT cause climate. It's having an atmosphere that causes a climate to exist. If a planet doesn’t have an atmosphere, it does not have a climate.
STATEMENT: “what causes the climate TO CHANGE is the sun”
EXPLANATION: Most of our energy comes from the sun. If the sun’s output goes down, in the absence of other factors that might be acting to counteract its influence, the Earth’s temperature would get cooler. If the sun’s output goes up, again if there are no other factors to counteract its influence, we get warmer.
The sun has certainly been responsible for climate change in the past.
It is thought to have contributed to the Little Ice Age, for example:
Lately, however, the sun’s energy has been decreasing since the mid-1970s. So, if the sun were the main driver for the Earth’s temperature change from the mid-1970s until now, we would be cooling. We aren’t though - we are warming. So although the sun has caused climate to change in the past, it is by no means the only factor that causes climate change, and in this case it is definitely not the dominant factor because we are warming instead of cooling.
The idea that the sun is driving climate change today is a very common
myth - so common, that it is one of the 3 myths I address in my recent
TEDx talk, starting at 7.25. Here is the link:
May 12, 2015
I generally agree with Katharine. We just interpreted the statement from Mr. Zimmerman differently. I interpreted his statement to mean that he thinks the sun is the primary (or only) driver of the climate, not the "cause" per se. If he literally meant "cause", Katharine's interpretation is correct.
In terms of her statement: "It's having an atmosphere that causes a climate to exist. If a planet doesn’t have an atmosphere, it does not have a climate." I generally agree... but it depends on how you define climate. If it is strictly defined as "average weather conditions", than she is correct. An atmosphere is required for weather... but if climate is defined as the expected temperature (or expected solar radiation, or other characteristics), than the moon has a climate (even though it does not have an atmosphere or weather).
I am not an expert on planetary atmospheres. However, Dr. Mark Lemmon (Dept. of Atmospheric Sciences) teaches a course on planetary atmospheres at Texas A&M. His course focuses on Venus, Earth, Mars, and Titan including the formation, *climate*, structure, dynamics and chemistry. Therefore, if you want to talk to an expert on planetary atmospheres speak to him.
Dr. Steven Quiring
Associate Professor & Graduate Director
Department of Geography
Texas A&M University
College Station, TX