h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Hi everyone,

I'd like to start a discussion on the forcing factors of climate change after reading a paper.

OK- the most widely accepted model of climate change seems to have CO2 as a forcing mechanism. You all know it as the greenhouse effect, and it seems to hold true for the past hundred million years with little problems- but those problems are big problems.

I read a paper this week that links the uplift of the Tibetian plateau with the onset of the current ice age. The idea is that the Himalayas changed the air circulation pattern to form the Indian Monsoon- this seems OK when you look at the change in the biology of the Indian ocean. The monsoon then starts eroding the newly exposed Tibetian plateau, sequestering CO2- all right, erosion of silicates, carbonate critters making their shells out of the ions, I can buy that. The only thing is, if that were the only thing driving climate change we should be heading into a "snowball Earth" condition right now because we're running out of CO2. In fact, the paper I just read says we're at a geological minimum.

Any thoughts?

What was the paper you read?

It always seems to me that the subject is a bit like the weather - impossible to predict accurately due to the influence of chaos.

The main argument has it that the carbon dioxide released by fossil fuels is the main problem. This carbon has been locked up for tens or hundreds of millions of years and in only 300 years we have released billions of tons of it back into the atmosphere whilst at the same time destroying one of the main sponges for carbon dioxide (rainforests). Interestingly the oceans are the biggest sink for carbon dioxide in two ways as I understand it. First carbon dioxide is soluble in water creating a weakly acidic solution. The oceans are VERY large in that respect and can cope with massive amount of carbon dioxide. The second is ocean life - phytoplankton which photosynthesize using carbon dioxide, coral and zooplankton that us carbon dioxide to build their skeletons.

As the oceans warm up they become less able to absorbe carbon dioxide. Global warming is all about there being more energy in the system because it can't radiate out into space due to carbon dioxide in the atmosphere. More energy means more active weather systems and melting ice caps. Melting ice caps change ocean currents. Smaller ice caps means less sunlight reflected into space which means more energy in the system... You get the picture.

One consequence of melting ice caps is the effect it will have on Europe. It is thought that the Gulf Stream will be pushed south or switched off altogether. Manchester (to pick a random example of a UK city) - relatively mild and wet is at latitude 53 degrees north. Toronto - warm in summer and very cold in winter is at latitude 43 degrees north and New York is at latitude 40 degrees north. Both these cities are south of Manchester and the Gulf Stream is the only reason Manchester is so mild and wet. Take the Gulf Stream away and the whole of the UK becomes as cold as Canada south of Hudson Bay!

I feel as though I might be telling you things you already know but I don't follow your post when you say that erosion of the Tibetan Plateau sequesters CO2. Surely the erosion of carbonaceous rocks releases sequestered CO2 into the atmosphere?

There is a good entry on Wikipedia here - http://en.wikipedia.org/wiki/Ice_age

Until later
turvy

The thing is, these rocks that are eroding aren't carbonates- they're uplifted and exposed silicates. The reaction is:

CaSiO3 + CO2 <-> CaCO3 +SiO2

That sequesters carbon in calcite, which then gets transported down to the ocean and gets included in all those little forams.