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Why CO2 lags behind temperature; another climate change skeptic myth explained

One of the most popular ‘theories’ currently being used by climate change skeptics, is that increased CO2 concentrations don’t cause temperatures to rise, but rather a rise in temperature causes CO2 concentrations to increase. They argue this means that humans can’t be responsible for the current warming trend, but this argument makes little sense when examined in detail.

The next time you hear your favourite global warming naysayer point out that carbon dioxide lags temperature by 800 years in the glacial record, don’t be surprised. That’s exactly how it must be.

There were no coal burning plants 21,000 years ago spewing carbon dioxide into the atmosphere.


In other words since we know that past changes climate were not caused by millions of people driving their SUVs to Walmart to get more milk, it is very likely that something other than increased CO2 emissions triggered past changes in climate.

What the fact that CO2 lags temperature in the past does suggest is that positive feedbacks exists in the climate systems. In other words the warmer it gets the more CO2 is released into the atmosphere by natural processes; this is in addition to to any CO2 that we release by burning fossil fuels.

The CO2 lag does not in any way mean that human emissions of CO2 are not responsible for the current warming trend.

That is, it doesn’t matter whether you put carbon dioxide in naturally or unnaturally, the fact remains that it is a greenhouse gas and traps outgoing longwave radiation.

What it does mean is that tackling climate change has much more urgency because small changes in climate (natural or otherwise) can trigger feedback systems that can greatly amplify this signal.

The last thing we need is natural systems working against our efforts to reduce atmospheric greenhouse gas concentrations.

14 Responses to Why CO2 lags behind temperature; another climate change skeptic myth explained

  1. Global Warming is a bunch of propaganda, and it is wholly inaccurate. We’ve been increasing in temperature for probably about a thousand years. Firstly, CO2 and CFCs are not the same thing at all. CO2 means that plants will flourish, CFC = plastic. Currently plastic is the most used material for just about everything. The CO2 from cars doesn’t mean anything. Heck, not even the CO really matters. (or the CEO, LOL) The next time you hear anything about CO2, just call it “AGG’ (Al Gore Gas).

  2. @ coward

    You show a profound misunderstanding of this topic, so I assume you didn’t read my comment policy. If you wish to continue posting here I suggest you read the links provided in the comment policy and at least get a basic understanding of climate change. Really it is the least you can do if you wish to be taken seriously.

    As for your specific comment, I’ll quickly respond to them

    We’ve been increasing in temperature for probably about a thousand years

    I suggest you read this report from the NAS. They concluded that “late 20th century warmth in the Northern Hemisphere was unprecedented during at least the last 1,000 years.

    Firstly, CO2 and CFCs are not the same thing at all. CO2 means that plants will flourish, CFC = plastic.

    I never claimed that they were the same thing, in fact I didn’t even mention CFCs in this post. Though they are both greenhouse gases. As for the notion that CO2 is beneficial to plants, while that may be true in some cases, the majority of the time there are other factors (nutrient availability, water…) that are far more limiting. Secondly many CO2 enrichment experiments have failed to show any benefits to plant growth rates, and may even retard growth. The link between increased plant growth and increased CO2 is tenuous at best.

    The CO2 from cars doesn’t mean anything.

    And you expect me to believe you when the IPCC the National Academies of Science from Australia, Belgium, Brazil, Canada, the Caribbean, China, France, Germany, India, Indonesia, Ireland, Italy, Japan, Malaysia, Mexico, New Zealand, Russia, South Africa, Sweden, the United Kingdom and the USA, the American Meteorological Society, American Geophysical Union, the American Association for the Advancement of Science, the Geological Society of London, the Geological Society of America, the Canadian Meteorological and Oceanographic Society, thousands of peer-reviewed journals, and even the American Association of Petroleum Geologists, say the opposite.

    In fact no scientific body of national or international standing is known to reject the basic findings of the human influence on the recent climate.

    If you wish to comment further please read the links provided in my comment policy. I have grown tired of debunking the same denier talking points over and over again.

  3. Dear Dan, in ten years time you will read this page and be profoundly embarrassed at what you wrote. In fact your arguments could be taken word for word to prove that climate change is not anthropogenic.

    I am a true skeptic. When someone says “Good morning” to me I look out the window to see if they’re telling the truth. I am skeptical about CAGW and I am skeptical about climate change skeptics. That’s why I landed on this page; it’s because I’m looking for convincing evidence that the CO2 lag is flawed. And I’m afraid that I neither found evidence, nor was I convinced.

    But thank you for the basic courtesy in calling us “skeptics” not “deniers.” Idiots like Greenfyre are only showing their own lack of intellectual and moral capacity when they use the derogatory term.

    • What do you mean the CO2 lag is flawed? Somehow I doubt you were referring to this.

      But regardless we know of the warming effect of CO2 from its basic radiative properties. Something that has been known for about 150 years!

      It doesn’t matter if humans add CO2 to the atmosphere or if it is added by natural processes the radiative properties, and thus the effects on the climate, of CO2 remain the same.

      When someone says “Good morning” to me I look out the window to see if they’re telling the truth.

      ugh, you must be insufferable!

  4. i am following this GW debate for a long time and this point is in fact one of the few that i side with the skeptics until i know better. Too many AGW website claim to debunk this “myth”. they say warming is not initialed by CO2 that’s why temp. goes up first. then after temp goes up, CO2 starts to go up which causes more warming in a basic positive feedback scenario. nice and good. what they don’t explain (and you don’t explain here) is why temperature goes down first at the end of the warming period despite the fact that CO2 is at its maximum value. if CO2 is lagging temperature in BOTH ways it means it cannot be the main driver of temperature in either direction. I know for fact that CO2 is a heat trapping gas but your argument to explain the lagging is not convincing if CO2 lags temperature in both ways.

    Sami

  5. i mean i side with them only on this point :-) since the mainstream explanation of this point did not make sense to me. I am not denying GW or against the mainstream position.

    • I still don’t understand your position but whatever.

      The simple answer is that CO2 is one of many climate forcings If the temperature drops while CO2 is at high concentrations in the atmosphere it is because some other forcing (a change in the earth’s orbit for example) is cooling the climate.

  6. So what method is employed to determine that part of the temperature increase that would have been caused by the trigger alone assuming the difference would be the carbon dioxide amplification.

    • There are many ways to estimate the size of a particular forcing. In regards to ‘wobbles’ in the earth’s orbit we have a pretty good idea of how much more or less radiation hits the earth as our orbit changes slightly.

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