Pop Quiz: Climate Change
Time for another pop quiz, this time on climate change. Here are the questions; the answers are given below [1]:
Climate is an interesting thing. In order to understand it, you need to combine physics and chemistry with biology and geology and you need to apply copious amounts of skull-splitting mathematics [2]. You are using spatially and temporally limited measurements to make extended predictions about a famously chaotic system. As a result, there are a lot of oversimplifications that creep into the discussion and make it more difficult for the general public to understand what is known and why it matters.Q1: When was the last time that the average temperature was as high as it is now?
Q2: CO2 is at 382 PPM. What is the highest level it has ever been?A) Never; this is the hottest it has ever been, thanks to climate change
B) Never; this is the hottest it has ever been, but climate change has nothing to do with it
C) About 5,000 years ago
D) About 3,000,000 years agoQ3: Polar bears are in danger because the Arctic ice is melting.A) 382 PPM; we have set a new record
B) 3,000 PPM
C) 900,000 PPMQ4: CO2 is the only greenhouse gasA) True, they've never had to face this before
B) False, they are in trouble because their habitat is being encroached by man
C) False, they are in no troubleA) True
B) Not true, but the other gases are insignificant compared to the effects of CO2
C) Not true, the effects of other gases are about equal to that of CO2
D) Not true, but we aren't sure what the relationship between the various gases and climate change is
Let's start off with the question of temperature. Today, the average temperature [3] of the globe is about 0.5 C above "normal". However, during the Holocene (5,000-9,000 years ago), the average global temperature was even higher than it is now. The temperature during the late Pliocene (~3,000,000 years ago) was also higher than it is today. We know this from a variety of sources, the best known of which are the oxygen isotope ratios. The change in temperature comes from a variety of factors, including changes in the Earth's orbit (Milankovitch cycles), changes in the amount of energy the Sun emits, changes in the location of the continents [4], changes in vegetation [5], and (of course) changes in the Earth's atmospheric chemistry. Of these factors, we have had the most influence on the last two.
We have changed the vegetation in ways both large (e.g., the Colorado River) and small (e.g., Roundup). But it could be argued that we have had an even larger impact on the chemistry of the atmosphere. We have added radioactive materials [6], we have added complex chemicals [7], and most notably we have added CO2. The Keeling curve is the best known record of the level of CO2 in the atmosphere, but it is not the only one. This is good, because Keeling didn't start his work until 1958! In addition, we have ice cores that contain records of both CO2 (from air bubbles trapped in the ice) and temperature [8] (from the oxygen isotope ratio in the water of the ice) extending back nearly 800,000 years. Before that, we have a series of proxies for both temperature and CO2.
What they show is that the temperature has often been much higher than it is now, and that the CO2 level has increased when the temperature has gone up. During the Cretaceous (145.4 - 65.5 million years ago {MYA}), temperatures were about 4 C higher than now on average, and the CO2 level was about six times higher than it is now. More recently, during the Holocene Climatic Optimum [9] about 5,000 years ago, temperatures were about 2.5 C higher than they are now and CO2 levels were similarly increased. Thus, the Earth has been hotter than it is right now; it has even been hotter in historical times than it is right now. Similarly, the Earth has had higher levels of CO2 than those we see today; it has even had higher levels of CO2 than we expect to see in the next century.
So why all the fuss? If this has happened before, then we don't need to worry about it, right? Wrong. The problem is that the last time an organism had this strong an influence on the Earth's atmosphere, it significantly changed the makeup of life on Earth [10]. We already see some evidence of this change happening now. However, not every extinction we see is caused by climate change - not even every anthropogenic extinction.
Take, for example, the poor polar bear. Right now, it is the poster child for endangerment due to climate change. However, polar bears have been around for about 200,000 years which means that they were here during the Holocene Climatic Optimum. So they've seen temperatures even higher and ice levels even lower than what we see today. So why are they endangered? Simply because the last time this happened, there weren't many other competitors for their niche and the polar bear was able to adapt. Today, the polar bear competes for land and food with the most vicious predator on the planet - man. Thus, the polar bear cannot retreat onto the land when the ice melts because we've taken all of the good spots. And it can't hunt moose instead of seals, because we've taken all the good ones. And so on. Unfortunately, those who would rescue it hurt their cause by oversimplifying and saying that the polar bear is threatened due to climate change. As a result, folks who would deny that climate change will change life on Earth [11] can seize on the motes in our eye while ignoring the beams in theirs.
And there are plenty of motes to seize on. For example, the focus on CO2 as a greenhouse gas [12]. Though it is the most prevalent greenhouse gas, and the one that is most intrinsically linked to mankind's efforts, there are others. And some of the others are even more effective at increasing the greenhouse effect. There is methane (CH4, which is a natural byproduct of digestion for critters from no legs (phytoplankton) to four legs (cattle) to n legs (creepy-crawlies). It is 20 times more effective at trapping heat than CO2; fortunately it decays rapidly in the atmosphere into CO2. Unfortunately, there are great stores of methane locked in clathrates (aka "gas hydrates") just offshore and locked in the tundra. If temperatures increase enough, this methane may be "burped" into the atmosphere rapidly, leading to an increase in greenhouse conditions [13]. Another greenhouse gas is water vapor, which acts both as greenhouse gas and (when it condenses into high-level clouds) as a cooling agent. The sheer volume of water in the atmosphere gives it a larger contribution toward warming than CO2 has. And, in one of those funny practical jokes that Mother Nature likes to play on us, increased temperatures can increase the ability of the atmosphere to hold water which then leads to an even stronger greenhouse effect and even higher temperatures.
Another favorite is the instability of climate models. Even today, we still don't know what happens to about 1/3 of the atmospheric CO2. We know it goes somewhere, because the amount isn't building up as quickly as it should. But where does it go? Favorite candidates are peat bogs, northern forests, and "missing" primary productivity. With a hole this big in the model inputs, you can imagine what skeptics have to say about the outputs [14].
Which brings us back to the point of this pop quiz. Quizzes should be a measure of the student's learning. But they are also a measure of the quality of the teaching. And thus far, the quality of education on climate change has been dreadful (in both senses of the word). By making the overly simplistic statements and by covering up the good that will come from climate change along with the bad, those who would "educate" others on climate change do themselves and their cause a disservice. And that is never a good thing.
John
[1] But try to give your answer before reading the actual ones, OK?
[2] The math starts at tensor calculus and works its way up from there.
[3] We pass over the problem of deriving an average temperature for something that varies widely in heat input and output. In truth, most climatologists use heat (a measure of the energy in a system) rather than temperature (a measure of how that energy has excited a particular part of the system) and only convert to temperature at the last step. By watching how the heat flows in a climate model, they are better able to understand the system. For analogy's sake, consider traffic on the highway. You and I measure traffic in speed; when we get stuck in a jam, we slow down and so think the two are synonymous. However, civil engineers measure traffic in the number of vehicles (and have even found that decreasing the average speed can increase the amount of traffic that flows through, thus shortening a trip!). From their calculations, civil engineers can take the more fundamental measurement (number of vehicles) and convert it into a more mundane one (speed). Climatologists do the same with heat and temperature.
[4] High latitude continents tend to accumulate snow, which has a high albedo, which reflects more energy back into space, thus cooling the earth.
[5] Ignoring the obvious, there is also the shift from dark-leaved vegetation to light-leaved varieties famously modeled in Daisyworld and seen in the change from tropical forests to grasslands.
[6] Which have proven to be a boon to anthropologists, as they allow a more precise dating of recent artifacts.
[7] Such as the CFCs that were widely hailed as a godsend in the 1930's (because they replaced even more dangerous chemicals in refrigeration units and made home fridges possible). After discovery of the ozone holes and banning of CFCs, their concentration in the atmosphere has begun to drop off and is projected to return to 1980 levels by 2060. This quick turnaround unfortunately makes some people think that we can have the same effect on CO2; nothing could be further from the truth. CFCs are naturally unstable in the atmosphere (which was the problem - they reacted with something we wanted to keep!), whereas CO2 is naturally stable. So the CFCs go away quickly and the CO2 is here to stay.
[8] Yes, I know I said that they use heat and not temperature [3]. But here the proxy records temperature (because the oxygen isotope ratio changes with temperature) and has to be translated into heat. This is typically done with modern analogs to provide a baseline for the relationship. Hey, nobody ever said this would be easy!
[9] Which, translated from the science-ese, means "Recent freakin' hot time". Honestly.
[10] Not that I'm complaining! I happen to enjoy breathing, thank you very much, and am grateful to those little slime-buckets that make it all possible. (It is a common mis-perception that trees provide all of the oxygen to the atmosphere. Actually, they provide only about 15%; more than half of the Earth's atmospheric oxygen comes from the ocean's phytoplankton. Were every tree to die, we would still breathe quite happily, thank you.)
[11] Believe it or not, there are those who do so. They run the gamut from denying that CO2 is even a greenhouse gas (Hello! Venus, anyone?) to denying that the temperature has changed at all to denying that there will be effects from the change in temperature.
[12] We'll pass over the "volcanoes make more CO2 than man" bit, as that is just silly. A quick check of the numbers shows it to be false. But then, these folks use numbers the way Humpty-Dumpty used words.
[13] I.e., the entire Earth will begin to feel like a fraternity on the afternoon that the A/C quits working.
[14] "Garbage in, garbage out" is about the kindest thing they say.
