There's plenty more evidence in the Met Office report to support global warming. But the question from critics remains: how can we be sure this isn't just a natural phenomenon? Scientists haven't done a good enough job of communicating how they distinguish human versus natural influences, says Hegerl. The answer lies in climate models — massive computer simulations that allow the scientists to project climate effects in various scenarios, including those in which humans do not emit any greenhouses at all.
"We go out of our way to check out other explanations — by assuming it's all explained by solar activity, or by solar activity plus volcanoes, or by combinations of any of the other natural forcings known to affect climate," says Hegerl.
According to the models, none of those combinations can produce the climate patterns currently being observed in the real world. Add the greenhouse gases that we know humans are generating (and which we've known since the 1800s tend to warm the Earth, all other things being equal), and the simulations finally come close to matching the real world. Its possible, albeit far-fetched, that the simulations are defective. It is even less possible that all of them (and there are many) are defective in the direction of overstating humanity's contribution to warming.
Report: The Case for Global Warming Stronger Than Ever - TIME
So much for the skeptic/denier meme that climate scientists aren't considering other sources of warming.
konradv- I think you are mistaken in your belief that no one could come up with a model that explains the present climate conditions without CO2 being the major driving force. the current models were written to emphysize CO2's effects and they do. mind you I dont believe that models that could be written to emphysize other factors would be any more reliable than the one we have now, just different.
There are only two ways that the atmosphere and oceans on the surface of the earth can warm up. One is an increase in the Total Solar Iradiance, the other is an increase in the retention of that heat.
The Earth reflects much of the TSI it receives from the sun. And radiates some of the heat away. As early as 1820, Joseph Fourier calculated that between the albedo of the Earth and the radiation of the heat at the surface, the Earth should have the oceans frozen nearly to the equator. He correctly hypothesized that something in the atmosphere was absorbing the heat. In 1858, Tyndall of England did the first mapping of the absorption spectra of greenhouse gases, water vapor, CO2, CH4, ect.
In the last 50 years, there has been a slight decline in the TSI. Yet, we have been rapidly warming. That leaves only an increase in the absorption of the reflected and radiated heat by our atmosphere to explain the increase in temperature. So, how would that occur?
In the last 150 years, by the burning of fossil fuels, we have increased the CO2 content of our atmosphere by 40%. We also have increased the CH4 by 150%.
Pretty damned simple, except for the many simpletons on this board.
We are in the start of the cooling period in the Milankovic Cycles, we have a decreased TSI, but we are rapidly warming. Every decade is warmer than the last. The only factor that would increase warming is the increase in GHGs in the atmosphere.
The simplicity is there. But the politics of preventing the inevitable results of a rapid warming and climate change is too great to address the problem. Too much money would be lost to the very wealthy of this nation and others. So we will do the grand experiment. At what point does the consequences become so great that even the willfully blind can no long deny the problem? And, realizing that no matter what we do, there is 30 to 50 more years of warming in the pipeline because of the lag in the warming of the oceans, that is how long we have to see how far the changes in climate will go.
