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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

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CO2 is not the only driver of climate

What the science says...

Select a level... Basic Intermediate
Theory, models and direct measurement confirm CO2 is currently the main driver of climate change.

Climate Myth...

CO2 is not the only driver of climate
CO2 is not the only driver of climate. There are a myriad of other radiative forcings that affect the planet's energy imbalance. Volcanoes, solar variations, clouds, methane, aerosols - these all change the way energy enters and/or leaves our climate.

Natural processes have determined Earth’s climatic history, but human industrial activities have introduced a new mechanism that is driving Earth’s climate future.

At any given time, the Earth’s climate is subjected to a myriad of natural influences.  The impact of each influence varies based on the magnitude of the natural change, the duration over which the change occurs, and whether or not that change is part of an overall repeated cycle.

Processes that have historically altered the face of the planet, like cycles in the Earth’s orbit around the Sun or shifts in continental tectonic plates, occur over tens of thousands to millions of years.  While not nearly as dramatic, the influence of solar, ocean, and wind patterns is much more immediate, but these effects generally alternate between warming and cooling over the course of months to decades in relation to their respective cycles.  Volcanic eruptions and impacts from celestial bodies, like asteroids, have a near instantaneous effect, but very few of these one-time events are of sufficient size to impact the global climate for more than a few years.

The industrial contribution of CO2 and other greenhouse gases to the atmosphere differs from its natural counterparts in fundamental ways.  This human influence is happening very rapidly, is not cyclical, and pushes the climate continually and relentlessly in the single direction of warming.

All of these influences, along with additional factors like land use changes, carbon soot and halocarbon emissions, and albedo variations, must be considered cumulatively to determine the net impact.

Over the last 30 years of direct satellite observation of the Earth’s climate, many natural influences including orbital variations, solar and volcanic activity, and oceanic conditions like El Nino (ENSO) and the Pacific Decadal Oscillation (PDO) have either had no effect or promoted cooling conditions.

Despite these natural oppositions, global temperatures have steadily risen throughout that time.

While natural processes continue to introduce short term variability, the unremitting rise of CO2 from industrial activities has become the dominant factor in determining our planet’s climate now and in the years to come.

Last updated on 11 September 2010 by Michael Searcy.

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Comments 1 to 7:

  1. cleanwater,
    you forgot to mention Ångström! It's a pitty. Apart from your random quotes and some standard shouting, you're welcome to discuss science, if you'll ever will.

    much too easy to copy and paste to leave garbage around ;)
  2. A great addition to this page would be a link to the page with the evolution of relative forcings over the past century or so. I just can't find that page at the moment.
    Response: Good idea. I may reshape the content to include the graph you're talking about but in the meantime, here it is:

    Separate global climate forcings relative to their 1880 values (GISS).
  3. Hot off the press from the Journal of Climate. Cloud data supports the higher end of the estimates of climate sensitivity :-/
  4. In the rediative forcing graph it shows "well-mixed greenhouse gases".  Is there a breakout of CO2, H2O, methane etc to show the relative importanct to the effect?

    and a related question, when we burn a fuel we get CO2 and H2O in a 3:4 ratio (typical). Since H2O is a more potent green house gas why all the hupla on CO2 and not the incresed H2O?


    [TD] Water vapor's concentration in the atmosphere is limited by temperature.  Putting more water vapor into the air than the air's temperature will support causes the excess water to drop out in about 10 days.  Therefore water vapor is a feedback to temperature increase, not a forcing.  See the rebuttal to the myth Water Vapor is the Most Powerful Greenhouse Gas.

  5. roosaw...  Here's the RF chart from IPCC AR5 that has them broken out...

  6. Reply to likeithot from here.

    Thank you for responding. Now what climate science actually states is that climate will respond to the net effect of all forcings. A huge amount of climate science also goes into understanding the internal variability that is inevitable when you unevenly heat an ocean-covered planet. Unfortunately, important processes (especially ENSO) for determining surface temperature defy predictive modelling. So, to quote the modellers - "climate models have no skill at decadal level prediction".

    Given these constraints, and the multiple forcings at work in climate, what then do you think the data should like that would convince you that the attribution to CO2 is accurate?

    If you are stumped, then perhaps you should read the IPCC WG1 chapter on attribution to see the approaches that have been done so far.

    One very important consideration to think about is that while surface temperature has a very high degree of variability, you do expect total ocean heat content to vary a great deal less in response to a constant forcing.

    And as an aside, if you dont want to have your comment moderated, then try reading and complying with the comments policy. If you want to bluster with uninformed rhetoric, then there plenty of sites on the internet that will welcome your comments. If you want to discuss the science, then welcome, and please study what the science says so we can have an informed discussion.

  7. likeithot wrote: "...for me to "believe" in AGW there would have to be a clear correlation between the beginning of human CO2 emissions and evidence of warming."

    Um, there is a clear correlation between the beginning of human CO2 emissions and evidence of warming... so long as you are looking at the full picture.

    If you look at the five minutes after the first coal power plant went online, no you won't see any correlation. Nor is it clear for the first decade or two. However, look at CO2 levels and temperature levels for the first hundred years since the industrial revolution and there is a very clear correlation. Both have gone nearly straight up at rates faster than anything seen previously in century level resolution proxy data.

    Thus, this argument amounts to, 'I will cherry pick a time frame too short to see the correlation and then pretend it is not happening'.

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