A reader asks about global warming...

A few days ago this email appeared in our inbox:

I am constantly bringing up the issue of global warming in conversation & have been telling people about the film An Inconvenient Truth - however I keep on getting the same response from people which is - while parts of the earth are getting warmer other parts are getting colder - so the global warming effect is cancelled out.

They never tell me which parts of the world are getting colder - are there parts of the world that are getting colder? If so where? And does this fit into global warming?

This was my reply:

Thanks for getting in touch and well done on your efforts to inform people about global warming. Perhaps the best thing I can do is point you to the notes on this at Wikipedia, which appears pretty authoritative and helpful:

http://en.wikipedia.org/wiki/Global_warming

You'll see that it's now very well established that average global surface temperature has increased significantly since pre-industrial times, almost certainly as a result of human activities (primarily fossil fuel combustion and deforestation).

I'm not aware of parts of the globe that are cooling - there *may* be - but there is no question of any global warming effect being cancelled out. As you'll see at Wikipedia, average global temperature has risen by about 0.6 deg Celsius in the 20th century - over the whole globe that's a huge amount of increased heat energy! It's that heat that drives the weather, storms, etc.

It may be that people have heard about the "global dimming" effect of airborne pollution that reflects back out to space some of the incoming solar energy. This has masked (not cancelled out) some of the global warming that would otherwise have taken place. Because of improved environmental regulations in many countries, airborne pollution (sulphate aerosols from power stations, etc.) is reducing. Good news in terms of better health, but it does mean that the dominant global warming effect will now become even stronger. Up till now, a kind of brake has acted upon global warming. But now the brake is coming off.

See: http://en.wikipedia.org/wiki/Global_dimming

Some important points to conclude:

It's not just about *average* effects such as the global average temperature increasing, sea level rising, etc. The more energy is in the climate system (more heat) - the more extreme phenomena will occur: severe storms, flooding, droughts, etc. Talking about just "warming" gives the impression that things will change gradually, in a linear manner. But the climate system can have positive feedback effects that suddenly accelerate the changes taking place: e.g. the potential melting of the permafrost in western Siberia (evidence is strong that this is already happening), releasing billions of tonnes of methane - a powerful greenhouse gas - into the atmosphere. That would truly have catastrophic effects.

Same goes for other possible "tipping points" (a buzz phrase much loved by politicians and the media but it's a proper scientific/engineering concept too), such as the melting of the Greenland or west Antarctic ice sheets. Yet another, is the possible weakening or even collapse of the so-called thermohaline ocean circulation in the North Atlantic, which includes the Gulf Stream and its extension, the North Atlantic Drift, which moderates the climate of western Europe. In a warming world, the ocean "pump" that drives this ocean circulation (the pump is the sinking of cool, saline water at high latitudes, which then "drags" up warm water from Florida) would falter. The temperature in western Europe would then drop by 5-6 deg Celsius - even as the rest of the world warms - a huge decrease that would have massive consequences for us. In fact there is evidence in a paper published in Nature by colleagues of mine last December that the Gulf Stream has already weakened by around 30%. Is this a longterm trend or part of a natural, decades-long cycle? We don't know yet - we need to keep monitoring what's going on - but there is lots of mounting evidence (e.g. Arctic sea ice cover not recovering every winter) that observed changes match very closely those that are predicted in a warming world by advanced computer models of climate.

best wishes,
David Cromwell

P.S. I haven't seen Al Gore's film but by all accounts it's very good on the climate science.

Climate change, ice sheets and rising sea levels: an exchange with a reader

I received the following on March 8, 2006 from a Media Lens reader who'd previously told me he thinks "evolution is probably the most sucessful theory peddled as fact". This time the topic is climate change. First, his email, followed by my response.

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In several of your alerts you refer to the present changes in climate as possibly being terminal. I discussed this with my son who commented as follows:-

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I'm not sure why the majority of scientists are that worried about a rise in temperatures considering that they are mostly evolutionists and would tell you that the earth has seen several much warmer periods in the past e.g. most of the rocks in Antarctica reveal tropical species once flourished there, as do many fossils found inside the Arctic circle. Melting ice sheets over water such as are found around the north pole won't change sea levels at all -just put a few ice cubes in a glass, mark the water level with a felt tip, and then mark it again once they have melted. Its the same due to the initial displacement caused by the ice.

When the vikings first arrived in Greenland, the climate was temperate and the land green with pastures, hence the name. The ice sheet has grown a lot over the last few centuries without any effect on sea levels. At the time of the viking expeditions, France and Britain were still seperated by the Channel.

When the earth cooled down, the Vikings made an exit from Greenland due to decreasing agricultural productivity. When it was warmer conditions were better to sustain their society.

Another thing to consider is that much of the far north is covered in permafrost and tundra, rich frozen organic material that is not forming now but was formed during a warmer period. When the northern latitudes were warmer, there was MORE biomass, not less. Look at how many mammoths there are buried in the tundra in Siberia, animals that require an enormous amount of food, which does not grow there now, but did in the past when the climate was much warmer, a possible 10 degrees warmer than today.

All this tells me that a rise in global temperatures does not lead to a reduction in biomass, but an increase. Why has this not been mentioned much in the debate, considering how fiercly the evolutionary viewpoint is pushed in mainstream media and education? The other studpid thing is that most climatoligists tell us that we are actually in an ice age at the moment. I agree with that to some extent. So why the panic?"
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Would you care to respond?


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March 9, 2006

Hi [Name withheld],

Thanks for getting in touch. Perhaps I may respond by referring you to some online resources for now. The Sir Alister Hardy Foundation for Ocean Science has produced on 'online encyclopaedia' about the oceans and climate change. It's nicely done and can be seen at:

http://192.171.163.165/Climate%20Encyclopaedia/index2.html

In particular, on rising sea levels, please go directly to:

http://192.171.163.165/Climate%20Encyclopaedia/sealevelchanges.html

where you can see that:

"Rising sea levels are caused by thermal expansion of seawater as temperatures increase and increased inflow of freshwater from melting ice caps and glaciers.Melting of ice on the surface of sea water does not contribute as it was originally formed from seawater. If all glaciers, the Greenland Ice sheet, the West Antarctic Ice sheet or all ice sheets melted they would lead respectively to increased sea levels of ~0.5 m, ~6 m, ~8 m or >80 m. It is to be expected that the recent rapid rise in global sea temperatures will have led to an increase in sea level rise from thermal expansion and there is clear evidence of major retreat of glaciers."

The info at Wikipedia also seems pretty reliable and up to date:

http://en.wikipedia.org/wiki/Sea_level_change

Or, if you really want the meaty stuff, go straight to the IPCC report from 2001 (though indications since then indicate *increased* threat of climate chaos) here:

http://www.grida.no/climate/ipcc_tar/wg1/408.htm

As for whether we are currently in an ice age or not (last glacial maximum was around 21,000 years ago), definitions vary. See:

http://en.wikipedia.org/wiki/Ice_age

As for why rising global temperatures and their related effects represent such a huge threat for humanity and ecosystems generally see this article by Mark Lynas:

http://www.marklynas.org/wind?document=34

One threat is the possible shutdown of the North Atlantic ocean 'conveyor belt' referred to here:

http://www.marklynas.org/wind/document/17.html

Hope these help.

best wishes,
David Cromwell
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