Friday, January 13, 2012

The Fire Next TIme

...the heavens shall pass away with a great noise, and the elements shall melt with fervent heat, the earth also and the works that are therein shall be burned up...2 Peter 3-10, KJV.

Astrophysics and biblical prophecy agree - hot times are coming - really hot. At some point during the next two billion years, the gradual warming of the Sun as more and more helium "ash" accumulates in the center will cause a runaway greenhouse effect as more and more water vapor accumulates in the atmosphere until the oceans boil.

At that point, it's game over. The temperature will rise to about 1400 C and stay there until nearly all the hydrogen in the atmosphere has been lost to space, at which point old Terra will become another carbon dioxide furnace like Venus - not as hot as 1400 C but still plenty hot.

There is the question of when. Could we accidentally accelerate the day of doom into the present by dumping a heck of a lot of CO2 in the atmosphere? Jim Hansen thinks so, but others aren't so sure.

From Technology Review's Physics archive blog:

But that raises an important question: is it possible that we could trigger a runaway greenhouse effect ourselves by adding carbon dioxide to the atmosphere?

According to the climate scientist James Hansen, that's a distinct possibility. A couple of years ago, he wrote: "If we burn all reserves of oil, gas, and coal, there's a substantial chance that we will initiate the runaway greenhouse. If we also burn the tar sands and tar shale, I believe the Venus syndrome is a dead certainty."

Today, Colin Goldblatt at the University of Victoria in Canada and Andrew Watson at the University of East Anglia in the UK, publish an interesting analysis of this question and, while they are nowhere near as pessimistic as Hansen, their conclusion is not entirely re-assuring.

Here's the background. The fear is that adding carbon dioxide to the atmosphere is warming the planet and increasing evaporation from the oceans. The extra water vapour, itself a greenhouse gas, causes more warming and more evaporation in a vicious cycle of temperature increases that eventually result in the ocean boiling away.
...
Goldblatt and Watson have an answer: "The good news is that almost all lines of evidence lead us to believe that it is unlikely to be possible, even in principle, to trigger full a runaway greenhouse by addition of noncondensible greenhouse gases such as carbon dioxide to the atmosphere."

But there is an important caveat. Atmospheric physics is so complex that climate scientists have only a rudimentary understanding of how it works. For example, Goldblatt and Watson admit that the above conclusion takes no account of the role that clouds might play in this process.

And scientists' ignorance of the processes at work raises a significant question mark. As Goldblatt and Watson put it: "Is there any missed physics or weak assumptions that have been made, which if corrected could mean that the runaway is a greater risk? We cannot answer this with the confidence which would make us feel comfortable."

Not that any of this will concern the religious and other crackpots.