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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 main driver of climate change

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.

Basic rebuttal written by Michael Searcy

Update July 2015:

Here is a related lecture-video from Denial101x - Making Sense of Climate Science Denial

Last updated on 15 July 2015 by pattimer. View Archives

Printable Version  |  Offline PDF Version  |  Link to this page


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Comments 51 to 59 out of 59:

  1. billev @50, try reading the graph @45 (reproduced below).  You will clearly see the observations are labelled as the GISS LOT five year running mean:

    For comparison, here is the GISS Land Ocean Temperature Index, as produced by NASA:

    You will notice that the red line is labelled as the 5 year running mean, and matches the five year running mean as I have produced it. 

    So, if you could not find a temperature series matching mine, it means only that you did not look very far, or that you did not recognize a line clearly labelled as a five year running mean to be a five year running mean.

    As to the trend, in the GISS LOTI, 2002 equals the anomaly of 1998 (which was then the record anomaly), but was exceeded in 2005, 2006, 2007, 2009, 2010, 2012, 2014, 2015, and will be in 2016.  Of those years, 2005, 2010, 2014 and 2015 set new records, as will (almost certainly) 2016.  The trend from 2002 to 2015 is 0.124 C per decade, which rises to 0.168 C/decade if you include the first 4 months of 2016.

    You may not want to include 2015 and 2016 as El Nino years, but that does not explain why you don't want to exclude the 2008, 2011, and 2012 which were all near record breaking La Nina years.  Of course, if you do want to exclude those years, it begs the question why you are looking at the trend from 2002 at all.

    To call that a "pause" is to show abysmall ignorance, or to lie.

    I did not answer your question @46 because, IMO, if you want to start running a conspiracy theory about global temperature records (which appears to be what you are angling for), I expect you to do it explicitly and on topic.

  2. billev@50:
    "....and they indicate a pause in warming starting about 2002."

    What pause?
    As Glenn explained in @28, ocean heat content is a much better indicator of global warming than atmospheric temperature, at least in the short term (a decade or two). If you study the chart he posted, you will find that the ocean warming from 2002 to 2015 was about 40% faster than in the previous 13 years, from 1989 to 2002! So, what pause are you talking about?

    As this thread is about CO2 vs other drivers of the climate, I want to include this chart (from Hansen & Sato 2004, "Greenhouse gas growth rates") which shows the annual increase of forcings from the well mixed greenhouse gases since 1950. Note that CO2 was less dominant a few decades ago because the contributions from methane and CFC’s were much larger.

    Well mixed greenhouse gases

  3. Billev, if you found a 20-year "pause" in the global mean surface temperature trend, what would you make of it?  

    1. Would you draw conclusions regarding the physical nature of the climate system? (e.g. the greenhouse effect does not exist)

    2. Would you conclude that global warming has stopped?

    3. Would you conclude that scientists are engaged in fraud, because clearly this is some sort of natural pattern?

    4. Would you respond thusly:  "Given that the greenhouse effect is extremely well-supported, and given that humans are indeed continuing to dump stored carbon into the atmosphere at an unprecedented rate, and given that ocean heat content continues to increase unabated, I wonder what's causing this pause in the surface temperature trend.  I'd better take a closer look at the physical mechanisms involved." 

  4. "Has there ever been any testing to examine the relationship beween the temperatures measured by the official measuring sites and the surface temperature at those sites?"

    I cant understand what you mean here. An official surface temperature sites measures the surface temperature at that site?

    Note the intricacies of local temperature variations at a site are removed for climatic purposes by looking at anomalies not absolute temperature. Defining absolute surface temperature is extremely difficult and not a lot of use.

    Ie, a 0.5C temperature rise, is a change in averate temperature of 0.5C from some baseline. Local surface temperatures vary enormously over short distances, but changes in temperature anomaly are consistant across 1000s of kilometers. (ie if it is warmer than usual in your city it is generally warmer than usual in the neighbouring city). The classic work on this is Hansen and Lebedeff 1987, but it rests of decades of earlier research on how best to measure temperature.

  5. Billev: I inadvertently deleted your prior two comments. Please repost them.

  6. Here are Billev's last two posts copied from the deleted comments bin where they were accidently sent by JH.

    4:13 am May 31:

    "The fact that CO2 absorbs heat is not the issue. The issue is whether the level of CO2 present in the atmosphere is sufficient to cause the warming the Earth has experienced since 1880. What form of measure has been employed to positively link the CO2 exisisting in the atmosphere to the warming of that atmosphere?"

    4:21 am May 31:

    "michael sweet @48, why is a "good argument" about the small level of CO2 in the atmosphere worth much. What is needed is an actual measurement of atmospheric CO2's role in the Earth's warming not an "argument".

  7. Billev:

    What do you want measured about CO2's role in Earth's warming that has not already been measured?  In 1896 Arrhenius calculated the effects of CO2 and predicted the increase in temperature.  He took the absorbtion lines for CO2 and combined that data with the measured lapse rate to make his calculations. His calculation is similar to the high end of the IPCC range today.   He also predicted that the night would warm faster than day, winter faster than summer, faster over land than water, faster in the Northern Hemisphere than the Southern and fastest in the Arctic.  He did not predict that the Stratosphere would cool as the Earth warmed because the Stratosphere had not been discovered yet.  You are 120 years behind scientists.

    Tom Curtis has posted hundreds of graphs that show the effect of CO2 in the atmosphere.  You have to say what effect you are not satisfied has been measured yet for me to respond.  I suggest you use the search function in the upper corner to find posts that describe the data you want.

  8. Billev seems to repeating himself because he doesnt like the answer - scientists measure the CO2 contribution to surface radiation by measuring it both at the surface and at top of atmosphere. It is positively tied to CO2 by the spectral signature. However, Billev seems to be contending that somehow this measured increase in radiation, positively identified to be from GHGs, has not be proven to actually heat the surface!! You can demonstrate that radiation in that frequency will heat a surface in a lab, (must do so by Plancks law) but apparently that is not good enough.

    Again Billev - stop avoiding the question and tell us what you think is heating the ocean and why this heat increase matches the GHG radiation?

  9. Chiming back in again....

    Billev's posting pattern is one of repeated "Just Asking Questions". I have yet to see him give any sort of indication regarding just what sort of "proof" he would accept, and I have yet to see him give any sort of detailed explanation as to why the answers he has been given are unacceptable.

    I do not see BIllev's pattern as encouraging an honest discussion of the issues.

    One issue he keeps beating to depth is his claim that he doesn't believe that CO2 is in sufficient quantity to make a difference, being in low concentrations. With radiation transfer, the presence of radiatively-inert gases in the atmosphere does not dilute the radiative effects of gases that are active in the wavelengths in question. It doesn't matter if it is 0.03%, 3%, or 3% of the total - it's the absolute amount that matters. And it's enough to matter.

    In fact, radiative measurements of sunlight can be used to determine the total quantity of a particular gas. A very common example is ozone - instruments measuring UV radiation at wavelengths where ozone absorbs strongly can be used to get the total atmospheric O3 value. The original instrument for this was the Dobson spectrophotometer, and the current Rolls Royce version is the off-the-shelf Brewer spectrophotometer. The total quantity is what matters, not the concentration. (Where the ozone is does matter in terms of atmospheric response, but the absolute  amount can be measured regardless of whether it is spread evenly throughout the atmosphere or concentrated at one altitude.)

    It's like cyanide. If a few millgrams in a cup of water will kill you, a few milligrams in a bucket of water will kill you, too. Dilution is not your friend, until you've added so much water you can't drink it all in a short time scale.

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