"A warming signal has penetrated into the world's oceans over the past 40 years. The signal is complex, with a vertical structure that varies widely by ocean; it cannot be explained by natural internal climate variability or solar and volcanic forcing,
At least until one takes into account that Solar Radiation incident at the surface is acutually increasing sufficiently to account for the all the above and more. The problem being that the atmosphere appears to be reflecting less solar energy back into space allowing surface and ocean temperatures to rise.
To claim it is of Human origin is fine that being a rather general tag all for anything imaginable, cleaning up the air might even have a bit to do with that, but to attribute the rise in CO2/Greenhouse gas concentrations, is a real stretch.
but is well simulated by two anthropogenically forced climate models. We conclude that it is of human origin, a conclusion robust to observational sampling and model differences. Changes in advection combine with surface forcing to give the overall warming pattern. The implications of this study suggest that society needs to seriously consider model predictions of future climate change."
Which models? Those associated with clearing the atmosphere of particulate pollution as opposed to sensitivity to greenhouse gases? Or merely just more coincidence because rising global temperature has been going on since the Maunder Minimum of the solar cycle.
Lets get out models and causes straight here why don't we?
Which are we to address? Make clean air more dirty so the atmosphere goes back to reflecting more solar radiation back into space, or play with CO2, that has a squat 0.2oK per doubling of concentration, not having much to do with any substantive in global temperature since the little ice age.
Data Show Earth's Surface Is Brighter and Scientists Study Climate Link
Refering to three papers ( Pinker et al., Wild et al., Charlson, R., et al.) in the May 6, 2005 issue of Science
- Pinker, R.T., et al., 2005. Do satellites detect trends in surface solar radiation? Science, 308, 850-854,
- Wielicki, B., et al., 2005. Changes in Earth’s albedo measured by satellite. Science, 308, 825,
- Wild, W., et al., 2005. From dimming to brightening: decadal changes in solar radiation at Earth’s surface. Science, 308, 847-850,
which indicate the amount of incoming solar radiation reaching the surface of the earth has increased dramatically in the last two decades, attributable to clearing of the atmosphere reducing the reflection of solar (aldebo) radiation away from the earth's surface.
Here are the wattage changes reported in the may Science articles associated with that increasing solar component at the surface as opposed to your graphic of top of the atmosphere solar incidence:
Change in solar radiation absorbed by the earth from 2000 to 2004, estimated from low-orbiting satellite data, reported by Wielicki et al.: 2.06 W/m2.
Change from 1983 to 2001 in solar radiation absorbed by the earth, estimated at the surface by satellites, reported by Pinker et al.: 2.7 W/m2.
Change from 1985 to 2000 solar radiation absorbed at the surface, as measured at the surface, reported by Wild et al.: 4.4 W/m2.
If we average the results of Pinker et al. and Wild et al. for the period 1985 to 2000 we get 3.55 W/m2;
then adding the results of Wielicki, B., et al. from 2000 to 2004 of 2.06 W/m2 we get a total of 5.61 W/m2.
That is nearly 10 time the change in direct radiation effects reasonably attributable to greenhouse gas concentrations from 1985 to 2004.
The added forcing from increased solar radiation reaching the earth’s surface has contributed nearly 10 times as much energy as predicated for greenhouse changes. When compared to the overall forcing greenhouse be attributed all (natural and anthropogenic) increases in greenhouse gas concentrations since pre-industrial times, it’s four times larger.
Is it the solar component we need to worry about or the CO2 gas concentration component.
Do we now curtail our attempts to clean up the air of its particulate contaminates and burn more polluting fuels in less efficient manner, so we can worry over the 0.2oKC per CO2 doubling of greenhouse gas factors instead?
That said -- I was nonplussed when I first read your reply, because though I'd read about the global dimming "reversal", it hadn't occurred to me -- nor apparently in anything else written about it -- that the increase in surface incident solar radiation was an adequate alternative to GHG forcing.
The Hansen, Nazarenko et al. paper (BTW, for some reason my direct link to the PDF in FR doesn't work, but you can get to it via the Earth's Energy Imbalance article) is mentioned in the NYTimes article you linked. The NYTimes article says:
"Dr. Wielicki said his data supported a report last month by a team led by Dr. James E. Hansen of the Goddard Institute for Space Studies in New York. In a paper published on Science's Web site, Dr. Hansen and his colleagues said that much of the excess heat generated by global warming so far had been stored in the oceans. Even if no more greenhouse gases are added to the atmosphere, they said, the Earth will continue to warm by 1 degree Fahrenheit, as the heat in the ocean is released into the air.
Dr. Wielicki said the amount of energy coming from the Sun matched the gain in heat in the oceans reported by Dr. Hansen. "They should actually match and they do," Dr. Wielicki said. "It is consistent with the ocean heat storage that the oceanographers are seeing, and it is consistent with the climate models predictions of what the heat storage should be."
Reading that does not give the impression that the forcings in the Hansen Nazarenko et al. paper were highly inaccurate. But that didn't completely illuminate what the effect might be, so I also went back to this article:
Global dimming may have a brighter future
which also discussed the articles you cited. While the actual article text didn't add a lot to my understanding, some of the commentary did. The key is -- the measurements indicate an increase in sunlight reaching the Earth surface -- they don't indicate a change in solar radiation incident on the Earth. (There are still some cloud/aerosol/albedo effects that have to be evaluated.) Here are the relevant comments:
"There is no such increase in solar radiation ,which has remained fairly constant, as the satellite obs show. What is happening is more likely an aerosol effect, which redistributes the radiation. The changes are so large that they cannot represent forcing directly, or we would be seeing obvious temperature responses, and would have seen obvious coolings before then.
"The point is, the effect is too large for it to be a direct loss/gain of radiation to the climate system - that would be obvious. So the incoming solar is not just being reflected out to space (at least, not totally or even largely - it may be partly) it must be being redistributed - either scattered and being absorbed somewhere above the surface, or some other effect."
"BUT these results have only just been published - they need to be digested and considered by the experts. Happily, they are about in time to feed into the next IPCC report AR4"
"Changes in daytime solar radiation reaching ground due to changes in atmospheric albedo by anthropogenic (short-lived tropospheric) aerosols are large, but they are compensated quite a lot by more thermal insulation (working day and night, for longwave infrared radiation}: clear sky insulates much worse. Amount of compensation is difficult to compute."
There's a subsequent point (which I won't provide in its entirety) that indicates change in the surface solar incident radiation would only warm the surface ocean because IR and visible only penetrate a few meters. Increasing surface radation would not warm the entire water column, so the heat storage in the ocean is a result of the climate warming process and not simply a result of increase solar insolation at the surface.
So -- while the changes are intriguing, and while there may be related cloud effects that have a climate impact, it doesn't appear that these results require a large-scale reassessment of the forcings used in the Hansen Nazarenko et al. paper or the Barnett paper. Moving on:
quoting Barnett et al.: "but is well simulated by two anthropogenically forced climate models. We conclude that it is of human origin, a conclusion robust to observational sampling and model differences. Changes in advection combine with surface forcing to give the overall warming pattern. The implications of this study suggest that society needs to seriously consider model predictions of future climate change."
to which you responded: "Which models? Those associated with clearing the atmosphere of particulate pollution as opposed to sensitivity to greenhouse gases?"
The models used in the study are: the Parallel Climate Model and the Hadley Centre Model (HadCM3).
Further research would be required to determine the full atmospheric aspects of the PCM, but the HadCM3 page says this:
"A penetrative convective scheme (Gregory and Rowntree, 1990) is used, modified to include an explicit down-draught, and the direct impact of convection on momentum (Gregory et al 1997). Parametrizations of orographic and gravity wave drag have been revised to model the effects of anisotropic orography, high drag states, flow blocking and trapped lee waves (Milton and Wilson 1996; Gregory et al 1998). The large-scale precipitation and cloud scheme is formulated in terms of an explicit cloud water variable following Smith (1990). The effective radius of cloud droplets is a function of cloud water content and droplet number concentration (Martin et al 1994). ... The atmospheric component of the model also optionally allows the emission, transport, oxidation and deposition of sulphur compounds (dimethylsulphide, sulphur dioxide and ammonium sulphate) to be simulated interactively. This permits the direct and indirect forcing effects of sulphate aerosols to be modelled given scenarios for sulphur emissions and oxidants."
Now, to answer this question:
Do we now curtail our attempts to clean up the air of its particulate contaminates and burn more polluting fuels in less efficient manner, so we can worry over the 0.2oKC per CO2 doubling of greenhouse gas factors instead?
I'd say both. Hansen has written that reductions in the black soot aerosol are still desirable because this is still a positive forcing -- he doesn't seem to consider the accruing increase in solar radiation resulting from such a reduction as a problem. However, he also believes that we (collectively) will reduce CO2 via technology improvements (which I think will accelerate in the wake of the KatRita storms), which he also views as an eventual necessity.
(I want to pursue the water vapor feedback more, if only to make sure that we understand the current state of the art. And I don't feel like typing in the abstract to the other paper until next week. Feel free to reply to this.)