Submitted by Doug L. Hoffman, Resilient Earth

Any competent researcher involved with the science behind climate change will admit that CO2 is far from the only influence on global climate. It has long been known that short-lived greenhouse gases and black-carbon aerosols have contributed to past climate warming. Though the IPCC and their fellow travelers have tried to place the blame for global warming on human CO2 emissions, decades of lies and erroneous predictions have discredited that notion. For anyone still clinging to the CO2 hypothesis, a short perspective article on the uncertainty surrounding climate change in Nature Geoscience has put paid to that notion. It states that not only did other factors account for 65% of the radiative forcing usually attributed to carbon dioxide, but that it is impossible to accurately determine climate sensitivity given the state of climate science.

In “Short-lived uncertainty?” Joyce E. Penner et al. note that several short-lived atmospheric pollutants - such as methane, tropospheric ozone precursors and black-carbon aerosols - contribute to atmospheric warming while others, particularly scattering aerosols, cool the climate. Figuring out exactly how great the impacts of these other forcings are can radically change the way historical climate change is interpreted. So great is the uncertainty that the IPCC’s future climate predictions, which are all based on biased assumptions about climate sensitivity, are most certainly untrustworthy. As stated in the article:

It is at present impossible to accurately determine climate sensitivity (defined as the equilibrium warming in response to a doubling of atmospheric carbon dioxide concentrations) from past records, partly because carbon dioxide and short-lived species have increased together over the industrial era. Warming over the past 100 years is consistent with high climate sensitivity to atmospheric carbon dioxide combined with a large cooling effect from short-lived aerosol pollutants, but it could equally be attributed to a low climate sensitivity coupled with a small effect from aerosols. These two possibilities lead to very different projections for future climate change.

All truthful climate researchers know these facts, yet publicly the party line is that catastrophic changes are in the offing and CO2 emissions are to blame. The perspective authors argue that only by significantly changing the amounts of these other pollutants and carefully measuring the impact on global climate over a period of several decades will science be able to figure out what is going on. “Following this strategy, we will then be able to disentangle the warming and cooling contributions from carbon dioxide and short-lived pollutants, hence placing much tighter constraints on climate sensitivity, and therefore on future climate projections,” they state. See chart below, enlarged here.

And they said it was all carbon dioxide’s fault.

Most of the factors under discussion have relatively short lifetimes in the atmosphere, several less than two months. We do know how the relative influences of these various substances (referred to by climate scientists as “species") may change in a warming climate. It is also not clear how to reduce short-lived species under present conditions but the uncertainties in atmospheric chemistry and physics must be resolved if Earth’s environmental system is to be understood. Again quoting from the paper:

Of the short-lived species, methane, tropospheric ozone and black carbon are key contributors to global warming, augmenting the radiative forcing of carbon dioxide by 65%. Others - such as sulphate, nitrate and organic aerosols - cause a negative radiative forcing, offsetting a fraction of the warming owing to carbon dioxide. Yet other short-lived species, such as nitrogen oxides, carbon monoxide and volatile organic compounds, can modify the abundance of both the climate-warming and climate-cooling compounds, and thereby affect climate change.

Quantifying the combined impact of short-lived species on Earth’s radiative forcing is complex. Short-lived pollutants - particularly those with an atmospheric lifetime of less than two months - tend to be poorly mixed, and concentrate close to their sources. This uneven distribution, combined with physical and chemical heterogeneities in the atmosphere, means that the impact of short-lived species on radiative forcing can vary by more than a factor of ten with location or time of emission. The situation is further complicated by nonlinear chemical reactions between short-lived species in polluted areas, as well as by the interactions of clouds with aerosols and ozone. These processes add further uncertainty to the estimates of radiative forcing.

Unfortunately, climate models neither accurately deal with local effects of these pollutants nor are the complex interactions among these substances understood. That not withstanding, the report is clear - CO2 does not account for even a majority of the warming seen over the past century. If other species accounted for 65% of historical warming that leaves only 35% for carbon dioxide. This, strangely enough, is in line with calculations based strictly on known atmospheric physics, calculations not biased by the IPCC’s hypothetical and bastardized “feedbacks.”

Of course, the real reason for the feedbacks was to allow almost all global warming to be attributed to CO2. This, in turn, would open the door for radical social and economic policies, allowing them to be enacted in the name of saving the world from global warming. The plain truth is that even climate scientists know that the IPCC case was a political witch’s brew concocted by UN bureaucrats, NGOs, grant money hungry scientists and fringe activists.

Now, after three decades of sturm und drang over climate policy, the truth has emerged - scientists have no idea of how Earth’s climate will change in the future because they don’t know why it changed in the past. Furthermore, it will take decades of additional study to gain a useful understand climate change. To do this, climate scientists will need further funding. Too bad the climate science community squandered any public trust it may have had by trying to frighten people with a lie.

Be safe, enjoy the interglacial and stay skeptical. Read full post here.

Mea culpa
Submitted by Doug L. Hoffman on Tue, 10/12/2010 - 16:58

I may well have misinterpreted the authors’ meaning and overestimated the reduction of CO2 driven forcing. Please note that I post two or three columns a week, reviewing data from dozens of papers -I’m bound to make an occasional error in interpretation. Not that this error was a gross one, I had the impact correct and was within an order of magnitude

My misinterpretation does not change the fact that CO2 can only be held accountable for 60% or less of the past century’s warming. Ramanathan et al., reported “Regionally, particularly in the tropics and subtropics with highly absorbing particles during the dry season, anthropogenic aerosols can decrease the average solar radiation absorbed by the surface by as much as 15 to 35W m2 and can increase the atmospheric heating, within the lowest 3 kilometers of the atmosphere, by as much as 60 to 100% (see “Aerosols, Climate, and the Hydrological Cycle,” in Science).

Even NASA has admitted that aerosols are more potent than previously suspected. A study led by Drew Shindell of NASA’s Goddard Institute for Space Studies says that, in the high latitudes the impact of aerosols (sulfates and black carbon) may account for 45% or more of the observed warming which has occurred in at the poles over the past three decades.

Also note that these changes are not accounted for by the IPCC findings. The IPCC rated the confidence in aerosol forcing very low, with very wide error bars, so they didn’t get included in the models. That is why these papers are noteworthy - they provide new numbers that were suspected by some, but not confirmed.

Icecap Note: Whatsmore, this totally ignores the other external and internal global factors like solar, ocean multidecadal cycles related to variations in the thermohaline circulation or ocean gyres.