The Real Issue in Climate
I know I hammer this home constantly, but it is often worth a reminder. The issue in the scientific debate over catastrophic man-made global warming theory is not whether CO2 is a greenhouse gas, or even the approximate magnitude of warming from CO2 directly, but around feedbacks. Patrick Moore, Greenpeace founder, said it very well:
What most people don't realize, partly because the media never explains it, is that there is no dispute over whether CO2 is a greenhouse gas, and all else being equal would result in a warming of the climate. The fundamental dispute is about water in the atmosphere, either in the form of water vapour (a gas) or clouds (water in liquid form). It is generally accepted that a warmer climate will result in more water evaporating from the land and sea and therefore resulting in a higher level of water in the atmosphere, partly because the warmer the air is the more water it can hold. All of the models used by the IPCC assume that this increase in water vapour will result in a positive feedback in the order of 3-4 times the increase in temperature that would be caused by the increase in CO2 alone.
Many scientists do not agree with this, or do not agree that we know enough about the impact of increased water to predict the outcome. Some scientists believe increased water will have a negative feedback instead, due to increased cloud cover. It all depends on how much, and a t what altitudes, latitudes and times of day that water is in the form of a gas (vapour) or a liquid (clouds). So if a certain increase in CO2 would theoretically cause a 1.0C increase in temperature, then if water caused a 3-4 times positive feedback the temperature would actually increase by 3-4C. This is why the warming predicted by the models is so large. Whereas if there was a negative feedback of 0.5 times then the temperature would only rise 0.5C.
My slightly lengthier discussions of this same issue are here and here.
Jonathan DuHamel:
One other point is rarely appreciated: greenhouse gases do not cause warming, that would imply that they are a source of heat energy which they are not. Rather, greenhouse gases delay cooling.
August 13, 2012, 10:37 amZachriel:
Coyote: All of the models used by the IPCC assume that this increase in water vapour will result in a positive feedback in the order of 3-4 times the increase in temperature that would be caused by the increase in CO2 alone.
It's not a bare assumption. There is substantial and recent literature on climate sensitivity. Using a variety of different methods, scientists have converged on a value of 2-5°C with 3°C the most likely value, but with significant uncertainty on the upper limit. Here’s a smattering:
Volcanic forcing
Wigley et al., Effect of climate sensitivity on the response to volcanic forcing, Journal of Geophysical Research 2005.
Earth Radiation Budget Experiment
Forster & Gregory, The Climate Sensitivity and Its Components Diagnosed from Earth Radiation Budget Data, Journal of Climate 2006.
Paleoclimatic constraints
Schmittner et al., Climate Sensitivity Estimated from Temperature Reconstructions of the Last Glacial Maximum, Science 2011.
Bayesian probability
Annan & Hargreaves, On the generation and interpretation of probabilistic estimates of climate sensitivity, Climate Change 2008.
Review
Knutti & Hegerl, The equilibrium sensitivity of the Earth’s temperature to radiation changes, Nature Geoscience 2008.
Jonathan DuHamel: One other point is rarely appreciated: greenhouse gases do not cause warming, that would imply that they are a source of heat energy which they are not. Rather, greenhouse gases delay cooling.
The greenhouse effect warms the surface and lower atmosphere, but cools the upper atmosphere.
August 13, 2012, 11:04 amhttp://www.zachriel.com/images/ar4-fig-3-17.gif
Zachriel:
Zachriel: The greenhouse effect warms the surface and lower atmosphere, but cools the upper atmosphere.
Warms, as in leaving more heat near the surface.
August 13, 2012, 12:10 pmDaublin:
It's a great interview all around. Here is one quote I really liked:
"By around the mid-1980s, when I left Greenpeace, the public had accepted most of the reasonable things we had been fighting for: stop the bomb, save the whales, stop toxic waste dumping into the earth, water, and air. Some, like myself, realized the job of creating mass awareness of the importance of the environment had been accomplished and it was time to move on from confrontation to sustainable development, seeking solutions."
In other words, the environmental movement has outlived its purpose.
Here is another one:
"I do not believe alarmism and fear are the correct responses even if our emissions are causing some warming. In particular I do not believe it makes sense to adopt policies that would obviously cause more harm that the supposed "catastrophe" that might be caused by warming."
I believe this would be pretty clear if it ever got into the public discussion. I wish it were more widely known just how ineffective the Kyoto Protocol would have been.
Overall, this is an environmentalist I can get behind.
August 13, 2012, 1:21 pmMingoV:
The real issue in the anthropogenic global warming debate is that there is no such thing as a greenhouse gas effect for the planet. The primary factor related to global temperature is the amount of solar energy reaching the lower atmosphere and the planet's surface. Increased atmospheric CO2 results in slightly more direct solar warming of the air AND slightly less direct solar warming of the surface. Since air and surface temperatures are in dynamic equilibrium, there is no change in the overall temperature of the planet.
@Zachriel: The models you mention are all crap because they don't include cloud formation. Assume that warming of the lower atmosphere occurs. Warmer air results in more evaporation of surface waters. However, because the air is warmer, the water vapor must rise to higher elevations before condensation and cloud formation occur. Higher elevation clouds produce less of a surface temperature blanket effect (more heat is lost from the surface at night) AND more of an albedo affect (more solar radiation is reflected away from Earth). These two factors result in cooling and in the restoration of temperature equilibrium. The increased water vapor does result in more direct solar warming of air (see above), but less solar warming of the surface. Those factors balance, and there is no net increase in evaporation. There is no multiplier effect, "sensitivity", or runaway atmospheric warming when cloud effects are taken into account.
August 13, 2012, 2:43 pmben:
The question I have is, given Earth's temperature has not run away in the 2 billion years life has existed here, how can 3-4 times positive feedback be compatible with long term stability of climate?
August 13, 2012, 7:26 pmmichael:
The amplitude of the solar radiation is 1,000
August 13, 2012, 9:45 pmmore then all the electrical energy produce on the face of the earth. That means that the main driver of the input of heat to earth is the Sun.
All of you are focusing on the heat resistance (or conductance)
instead of the heat source. A slight variation of the radiation of the Sun will result in great changes in the atmosphere.
me:
I thought the discussions around global warming were about who will get to rip taxpayers at large off the most with their actively traded CO2 certs?
August 13, 2012, 10:36 pmFred Z:
I thought there were some minor issues with the statistical significance of a few hundred years of samples for a system billions of year old, largely inaccurate and covering infinitesimal parts of the earths surface.
When my old stats prof said he had 'minor issues' with your work, it was time to switch to poli sci or sociology, or maybe just leave town.
August 13, 2012, 10:53 pmGil:
Gee, if feedback mechanisms couldn't possibly work then life on Earth wouldn't even exist and Earth would look much the same as Venus except will less cloud cover and being cooler.
August 14, 2012, 12:53 amZachriel:
MingoV: The primary factor related to global temperature is the amount of solar energy reaching the lower atmosphere and the planet's surface. Increased atmospheric CO2 results in slightly more direct solar warming of the air AND slightly less direct solar warming of the surface.
It's very simple to calculate that the Earth's average temperature without the greenhouse effect would be a chilly ≈-18°C rather than the balmy ≈+15°C that it is.
MingoV: @Zachriel: The models you mention are all crap because they don't include cloud formation.
They weren't models, but empirical measures using a variety of different methodologies.
ben: The question I have is, given Earth's temperature has not run away in the 2 billion years life has existed here, how can 3-4 times positive feedback be compatible with long term stability of climate?
Actually, the temperature of Earth has oscillated substantially over its history.
August 14, 2012, 7:33 amGil:
Obviously the ancient past must have been net carbon-locking is due to the fact that coal and oil exists - plant and animal carbon being compacted into the crust. Conversely, human activity is liberating the ancient carbon via burning coal and oil. There's also the issue of trapped methane and water being unlocked too.
August 14, 2012, 8:21 amMingoV:
Zachriel replied: "It's very simple to calculate that the Earth's average temperature without the greenhouse effect would be a chilly ≈-18°C rather than the balmy ≈+15°C that it is."
Another crock of bullshit. You obviously didn't understand my answer. As far as mean planetary surface temperature is concerned, there is NO difference between a solar photon warming a CO2 molecule in the lower atmosphere, a water molecule in an ocean, or a speck of soil on land.
August 14, 2012, 2:58 pmchembot:
As much as I hate to come to the defense of the warmists, angry ignorance does no service to the skeptical side of the argument. Zachariel is correct that without a greenhouse effect the mean temperature of the Earth would be well below freezing. This fact is uncontroversial and there a number of people on both sides of the issue who have some version or another of these basic climate facts easily available on their websites. If you don't believe the commenters here, perhaps you can take the word of noted skeptic Roy Spencer on this.
Also, it sure does matter whether a photon is absorbed by CO2 vs. Water vs CH4 vs. SF6 vs. CHFCl2. All of these species are very different in their chemical properties such as Absorption Spectra, Heat Capacity or reactivity (lifetime in atmosphere or conversion to differently absorbing materials). And continuing in this theme, land masses have very different albedo (reflectivity) depending on whether you are talking about desert vs. forest vs. icecap. These terrain reflect light and retain heat very differently from the ocean.
It is unfortunate that once an issue becomes politically charged (especially when it comes to science) both sides often descend to fighting ignorance with ignorance. Reminds me of a great old SMBC comic "My anecdotal evidence is loud!" "Mine is louder!!"
August 14, 2012, 7:08 pmbob sykes:
I wonder if Coyote would care to comment on the Vostock Ice Cores?
These indicate that over the last several hundred thousand years (and several ice sheets advances and retreats) that temperature changes precede carbon dioxide changes by 400 to 800 years. This suggests that temperature changes drive carbon dioxide changes and that something else causes temperature changes, eg. Milankovic Cycles. Note that temperature is falling when carbon dioxide is at its peak.
Of course, these are large-scale fluctuations and might not reflect the mechanisms of the small-scale fluctuation we are now experiencing. Also, they do not imply that there is no greenhouse effect, merely that it is secondary over the time scale of the data.
One way of dealing with this, and I have heard people say it, is that the Vostock data is simply wrong, that the sampling and analysis were somehow screwed up.
August 15, 2012, 4:50 amZachriel:
bob sykes: These indicate that over the last several hundred thousand years (and several ice sheets advances and retreats) that temperature changes precede carbon dioxide changes by 400 to 800 years. This suggests that temperature changes drive carbon dioxide changes and that something else causes temperature changes, eg. Milankovic Cycles.
There are multiple causes of climate change over Earth's history. Orbital variations are thought to be involved in geologically recent climate changes, along with various feedback mechanisms. In particular, when solar irradiance increases, this triggers the process of melting ice, which decreases the Earth's albedo, amplifying the warming. As the oceans are exposed, they release carbon into the atmosphere, again amplifying the warming trend. When solar irradiance decreases, this causes ice to form, increasing the Earth's albedo, amplifying the cooling. The oceans become locked under ice, trapping CO2, again amplifying the cooling trend. (Over longer trends, geological processes of ocean and rock scrub carbon from the atmosphere, while volcanoes emit carbon. So if the Earth were to freeze completely, the geological scrubbing would stop, and atmospheric carbon would increase until it triggered the melting process, restarting the scrubbing process.
These feedbacks help explain why Earth's climate tends to seesaw between warm and cool. It's a complex dynamical system with no single point of stability. Atmospheric carbon is both an effect and a cause.
August 15, 2012, 5:40 amTed Rado:
If the cost and disruption of accepting the CAGW hypothesis was minor, many would say "go ahead". However, to reduce CO2 by 80% would have a catastrophic effect on our industrial civilization. Furthermore, there is no viable alternative to fossil fuels (except for electricity generation). I read a piece by some enviroloony to the effect that "yes, they know there is no alternative, but if forced to do so, scientists and engineers would find a way". What rubbish! Jump out of an airlane and hope that someone will invent a parachute before you hit the ground.
In the CAGW crowd really wants to be useful, solve the problems of alternative energy. I do not see such solutions, except for nuclear electricity. The current crop of renewables are a joke. With free, forced, backup, they are still completely uneconomical. And, there are no viable backup or storage methods. (The enviroloonies don't want nuclear either.)
A little less zealotry and more careful study would be a blessing.
August 15, 2012, 9:23 amtomw:
Perhaps they should get that new Ryan T-shirt with the Obama-like colors and one word at the bottom:
Math
Hmmm?
Innumeracy is contagious, apparently.
tom
August 20, 2012, 10:55 am