This post is by Lisa Moore, Ph.D., a scientist in the Climate and Air program at Environmental Defense Fund.
In IPCC‘s Third Assessment Report (2001), scientists reported that carbon dioxide (CO2) and methane levels were higher than at any time in the past 420,000 years. In their latest report (2007), IPCC scientists raised the number to 650,000 years.
Last week, scientists again revised the number upward. New research shows that CO2 and methane levels are higher today than they have been in at least 800,000 years.
Here’s how they know.
The research, published in Nature, analyzes the atmospheric gases trapped in ice cores extracted from Antarctica. These ice cores are the oldest yet studied. In 2001, the 420,000-year old Vostok ice core from eastern Antarctica set the benchmark. In 2005, scientists analyzed a 650,000-year record from Antarctica’s Dome C. Now, drilling even deeper, scientists at Dome C have assembled an 800,000 year record of CO2, methane and temperature.
These are the main findings:
- CO2 and methane levels are higher today than they have been in at least the past 800,000 years.
- The strong correlations of methane and CO2 with temperature reconstructions are consistent back 800,000 years.
- The long-term cyclic changes in temperature, methane and CO2 that follow slow changes in Earth’s orbit are consistent back 800,000 years.
CO2 (red) is in parts-per-million (ppm); methane (green) is in parts-per-billion (ppb); temperature (black) is relative to the average of the past millennium. Reprinted by permission from Macmillan Publishers Ltd: Nature. "Windows on the greenhouse" by Ed Brook, Nature 453: 291-292, copyright 2008.
There are no surprises in the big picture, but more detailed analysis raises some intriguing questions. For example:
- Cold phases remain roughly similar throughout the 800,000 year record, but starting about 450,000 years ago, warm phases got warmer. Why?
- What accounts for the unusually low value for CO2 (172 ppm) about 667,000 years ago?
Scientists are already forming hypotheses about these and other questions. To help find answers, scientists have launched a new project to obtain a 1.5 million year record. That will mean drilling in locations with older ice because they’ve nearly reached bedrock at Dome C.
In the meantime, one thing is clear: Human activity has had an enormous effect on Earth’s natural cycle. It’s time to take responsibility for the damage we’ve caused and cap emissions.
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Can you explain to me why the glaciers in the US, New Zealand, Greenland, South Pole, South America, Asia and perhaps other places are growing, some at alarming rates? It appears also that the Arctic ice is also increasing. It does not seem logical, that if our planet is undergoing global warming, that the world’s glaciers, for the most part, are growing. I am not a scientist, but there is a great deal of controversy on this subject. It appears that some of this could be very political and not necessarily fact. It appears to me we need to find alternative energy sources, but in the meantime we better be building nuclear power plants, using clean coal technologies, and drilling the oil sources that we have, which are, as I understand it, many times greater than that of Saudi Arabia. Ethanol is not by itself a very good fuel. Like to get your thoughts.
Actually, ice is disappearing. For example, check out our post “Arctic Sea Ice Shrinking Unexpectedly Fast” and this animation of Arctic sea ice from the National Snow and Ice Data Center.
The IPCC devotes Chapter 4 of its Fourth Assessment Report to “Snow, Ice and Frozen Ground”. It’s a comprehensive review of all the changes we’re seeing due to global warming. Here are just a few excerpts: “Snow cover has decreased in most regions…. decline in annual mean arctic sea ice extent…. Mass loss of glaciers and ice caps…. thinning, reduction or loss of ice shelves…. The permafrost base has been thawing…. extent of seasonally frozen ground has decreased.”
Bill Chameides did a great series of posts about how we know humans are responsible for recent rapid global warming.
Fortunately, the main conversation among policymakers today is not about the science or whether to implement climate legislation, but how to do it most effectively. Environmental Defense Fund believes that the answer is cap-and-trade, and that the Climate Security Act is a strong start.
From the graph on the left above, the temperature peaks are similar. Looking at temp, it looks like we are peaking again, and could very well be heading down again.
And the ice caps at the south pole are growing. Maybe not at the north pole. And you keep treating the IPCC as gospel. Why then is there a petition of 30000+ scientists in this country alone that there is no convincing evidence that man is causing global warming, and that evidence shows that higher co2 and methane is actually beneficial??? And I was not convinced by Chameides’ weak arguments.
Disclosure: I have a MS is Engineering and am not affiliated with any group benefiting from carbon sales or use, political organization, etc. Just like to get to the bottom of things.
It seems to me that articles like this one don’t do a lot to help the cause; they don’t seem to hold up to close scrutiny. Specifically:
“CO2 and methane levels are higher today than they have been in at least the past 800,000 years.”
1) What meaurement methods are used? If actual measurements are used for current levels, then a comparison to ice core analysis is an apples-to-oranges argument, and not really valid.
2) I am not familiar with the details of ice core analysis. Are the analyses valid for short-term effects? Can we really tell what the levels were in individual years, or decades, or centuries?
“The strong correlations of methane and CO2 with temperature reconstructions are consistent back 800,000 years.”
1) Correlation does not necessarily imply causation. Possibly a fourth variable affects all three items shown here.
2) Although the scale makes it difficult, it appears from the graphs that temperature changes predate methane level changes, which predate CO2 level changes. Not a strong argument for CO2 and/or methane driving temperature change.
“The long-term cyclic changes in temperature, methane and CO2 that follow slow changes in Earth’s orbit are consistent back 800,000 years.
1) The fourth variable mentioned above. If all three variables follow “slow changes in Earth’s orbit” then it is even less likely that there is a causal relationship between them.
2) If this statement is true, it would (in my opinion) argue AGAINST any human activity being the cause of temperature change. If temperature changes have happened for 800,000 years, and follow changes in the Earth’s orbit, then what makes anyone believe that anything humans can do will alter that pattern?
“Cold phases remain roughly similar throughout the 800,000 year record, but starting about 450,000 years ago, warm phases got warmer. Why?”
Why, indeed. I would say, without reservation, that the answer to that question is NOT human activity. Again, it would seem to indicate that the phenomenon is a wholly natural one, and that nothing we humans can do will alter it. What happens, happens.
“What accounts for the unusually low value for CO2 (172 ppm) about 667,000 years ago?”
Environmental regulations of the government in place at that time? A precursor to the Kyoto treaty? I suspect, once again, that human activity did not contribute to this datum, one way or the other. Again, a fairly strong argument that climate change, CO2 levels, and other natural phenomena are exactly that: natural. Human beings affect such things only by virtue of being a part of nature.
Disclaimer: My degree is in electrical engineering, and I work for an environmental engineering company. I strongly believe in our mission, and in the need for environmentally friendly solutions, in and of themselves. I am not convinced that AGW is real or controllable, or that it is a reason, by itself, to do anything.
Well, here is something I find interesting. It would seem that the CO2/Methane temperature swing varies wildly and always drops back to EXTREMELY cold. What are we doing do stop this disaster that is very obviously overdue according to that chart?
The self-proclaimed scientists that pile onto these discussions are constantly whining about the IPCC because they can’t measure up to scientific evidence no matter how hard they try. “my degree is in electrical engineering” another failed university student. He makes the most moronic arguement ever heard and then makes the statement “CO2 levels are natural” because “humans are part of nature”.
Ever heard of physics? When you pump 16 billion tons of unasorbed C02 into the atmosphere yearly, you’re not talking about an occasional major volcano eruption, or a peaks after an ice age, where the earth has thousands of years to adjust, and where it has ALL its natural C02 aborbing mechanisms in place. It’s a sustained deliberate increase in global warming gases HUMAN CAUSED which has snowballing effect, along with human destruction of natural C02 absorption systems.
It’s called steady pumping of CO2 into the atmosphere by HUMANS at a faster rate than ever seen from natural occurences with humans destroying C02 absorption mechanisms. The southern oceans are saturated and can’t absorb. Land absorbing systems like forests are cut down. By ice core samples of hundreds of thousands of years any period before the Industrial Era was no more than 3.6 ppm per century. The current CO2 growth rate is close to 100 ppm per century, which is more than 20 times as fast.
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