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Jan 3 / Dave Schumaker

Climate Change – How We Know What We Know

Our only home. Image by Aaron Escobar.


In 1998, researchers in eastern Antarctica drilled one of the deepest ice cores that had ever been extracted. It’s called the Vostok ice core (named for where it was drilled, near Russia’s Vostok Antarctic ice station).

Researchers examine an ice core in Antarctica. Photo by Tas van Ommen.

Ice cores are significant in terms of paleoclimatology because scientists noticed that as snow falls year after year, it forms nice little stratified layers that are visible (you can see this in glaciers and such) to the naked eye. Trapped within these layers are small air bubbles that get trapped during heavy snow falls. As more snow accumulates, the pressure eventually fuses these layers of snow together into solid ice and the air bubbles are now permanently trapped in their respective layers.

These air bubbles provide an interesting snapshot of the atmospheric composition at the time they were trapped, in particular the ratio between two oxygen isotopes: O-16 and O-18 as well as the concentration of CO2 (as well as other potential greenhouse gases such as CH4) that are present in the atmosphere. The ratio between O-16 and O-18 is important because it can tell you relative temperatures between two different time periods (more info on how you can tell that is available here). And based on how much CO2 and CH4 is present, you can come up with concentrations in ppm.


The graph shows some interesting results. You’re able to see the relative differences in temperature changes in the past compared to present day, as well as the amount of CO2 in the atmosphere and how both of these things change over time.

Now you’ll also see an interesting correlation (and *this* is what has climatologists and geoscientists the world over worried about climate change). You see a VERY close relationship between the amount of CO2 in the atmosphere and the difference in temperatures. Higher temperatures correlate with a higher concentration of CO2 in the atmosphere, while lower temps correlate with lower concentrations. Hmm! Intriguing!

It’s interesting to note there also appears to be some sort of cyclic process involved as well, as you notice temperature highs and lows seem to have roughly a consistent amount of time between each cycle. It’s hypothesized that this is actually due to something called a Milankovitch cycle, which is the relationship between the Earth’s distance from the sun, orbital eccentricity, tilt of the axis and some other factors. When these all line up in a certain way, they appear to have HUGE effects on Earth’s climate (which might ultimately render the whole global warming debate moot).

Mauna Loa and CO2

In the 1950’s, an intrepid scientist decided to setup a laboratory to record the amount of CO2 present in the atmosphere as an interesting experiment. He setup his lab at 14,000 feet, way up on top of Mauna Loa. This was primarily because Hawaii is smack in the middle of the Pacific and far far away from really major cities that might contaminate or otherwise skew his readings.

This data is still being recorded today. Now comes the part that has everyone worried. His data since the 1950’s is showing an *exponential* increase in the amount of CO2 that is in the atmosphere. Cue graph!

Source: NOAA.

So if you look at that, you notice there is a crazy increase in the amount of CO2 that’s currently in the atmosphere. Some people have tried to explain it away using various arguments (such as volcanic explosions), but with the rapid rate of industrialization going on in the world, how much fossil fuel is being consumed and waste products that are going into the atmosphere, I really think it’s irresponsible to say that humans are not to blame for the increase in CO2 concentrations. Now, notice a distinction.

CO2 vs. Temperature

What we haven’t really seen since the 1950’s is a rapid increase in temperature that corresponds to the increase in CO2 (like we see in the Vostok cores). We HAVE seen an overall increase in temperature (1970’s ice age scares aside), but it’s by no means “as steep” as the CO2 concentration graphs.

This suggests that there may be something else that is responsible for global warming that isn’t obvious to us at the moment (or there is some sort of lag time between CO2 increases and temperature change).

Other Research Related to Climate Change

That said there, I definitely don’t think we should claim ignorance and play dumb until we know for sure what it going on. By then it may be too late. There are some interesting factors we don’t exactly understand though when it comes to controlling CO2 and other greenhouse gases. Among them is carbon sequestration in the ocean.

Though when you also look at CO2 input/output, you have a large amount of CO2 being taken up in plant material (such as rain forests), which then end up being slashed and burned. This has a two-fold effect since now you’re releasing all the trapped CO2 BACK into the atmosphere, as well as diminishing the ability of the forest to take in CO2 by making less forest.

There are some interesting experiments that have been done though. Some have argued that increased concentrations of CO2 will actually lead to healthier forests. An experiment trying to determine this was carried out by Duke University and it appears they have concluded it does… up to a point. Researchers in Texas concluded the same thing.

“We found that many of the plants’ physiological processes responded fairly linearly to increases in carbon dioxide, and plant production went up,” said Jackson. “However, production and soil carbon storage basically saturated above 400 parts per million, a CO2 concentration very close to the current one.

“For me, this was the most interesting part of the study, because it indicates that we are now right at a threshold where the benefits of extra CO2 may not be all that great.” Particularly important, said Jackson, were the measures of soil nitrogen availability. Soil bacteria metabolize organic matter, mobilizing nitrogen as ammonia and nitrate, which serves as the plants’ nitrogen nutrient source

Intergovernmental Panel on Climate Change – Fourth Assesment Report (Jan. 2007)

Though there is a definite swing in public opinion and research that is showing more and more that you actually can trace some aspects of climate change in the past 100 years to human activity. Look no further than the Fourth Assessment report (published in January of this year) put out by the Intergovermental Panel of Climate Change.

Based on all the latest research they’ve been able to review and synthesize, they believe with 90% confidence that current climate change can be attributed to humans and is the result of increased concentrations of greenhouse gases (such as CO2) present in the atmosphere.

Global atmospheric concentrations of carbon dioxide, methane and nitrous oxide have increased markedly as a result of human activities since 1750 and now far exceed re-industrial values determined from ice cores spanning many thousands of years. The global increases in carbon dioxide concentration are due primarily to fossil fuel use and land-use change, while those of methane and nitrous oxide are primarily due to agriculture.

And a few more tidbits from the report.

Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level.

Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations. This is an advance since the TAR’s conclusion that “most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations”. Discernible human influences now extend to other aspects of climate, including ocean warming, continental-average temperatures, temperature extremes and wind patterns

Unfortunately, the paper concludes that it may be too late to alter or prevent significant climate change due to the amount of CO2 currently in the atmosphere, but we may be able to mitigate it by enacting certain measures.

You can download a summary (PDF file) of the report from here.


I think it’s a bit foolish for people to still completely ignore human activity as a potential source of climate change. Sure, there are natural factors that can (and are) attributed to global warming, but the Vostok Ice Cores, data from Mauna Loa, foraminefera data from all over the ocean plus many other sources of data provide pretty compelling evidence that something is beginning to happen that may not completely be in sync with natural cycles.

Anyway, whether we are ultimately responsible for global warming or not, I definitely think something should be done about the rapid rise in CO2 concentrations and such. Besides, what do many people have against breathing clean air? ;)

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