Thursday, October 12, 2006

Global warming - Is it really happening?

Stop laughing at the back!

The problem with discussing global warming is that it almost immediately becomes theological.

In fact I can already see some in the environmental lobby preparing to burn me at the stake. Obviously they will only use wood from sustainable forests which encourage bio diversity that has not been transported too far.

A few days ago I came across this by LuboŇ° Motl and this by Iain Dale.

There is clearly a lot more we do not know about global warming than we do.

The first article by LuboŇ° Motl goes on about how global warming does not seem to be happening in the Southern hemisphere, while Ian Dale queried David Miliband's numbers on CO2 levels. These two things could be easily explained. The differing data on the Southern hemisphere may be because CO2 levels there are lower, and the differing CO2 numbers can also be explained because CO2 levels vary by time of year and region.

We hear so many things on the subject from "Were all doomed!" so we might as well not bother to "it's a myth" and all of it in either theological or ideological terms. That is not way to deal with a serious scientific matter.

Still lets try and look at it sensibly:

  • Is the world warming up?
  • If it is, is it man made or is the sun burning hotter?
  • Is there anything we can do?
  • Could global warming be a good thing?

Is the world warming up?

Well it looks like it is. We have had a series of hot summers, and it seems some glaciers are melting. However the planet is not as hot as it has been in the past.

Is it man made, or could the sun be getting hotter?

Possibly, or rather probably. Scientists think it is man made because they have been looking at CO2 emissions and concentrations of CO2 in the atmosphere. CO2 absorbs more heat from sunlight than either oxygen or nitrogen does, so the more of it there is about the more heat the atmosphere absorbs from sunlight. You can try an experiment at home. Get two similar clear plastic bottles and have one with only air in it, and fill the other with CO2, then put a thermometer in both and put them in the sun. The one with mostly CO2 will get a lot warmer a lot quicker.

CO2 levels also vary by season, and place as levels of consumption and production vary by economic activity and plant growth.

Could the sun be getting hotter?

Well, it could be. I don't think we know enough about the cycles of the sun to be able to be anything like conclusive. The question is surely so what?

The planet would be ice bound with out any CO2, so it follows that our behaviour can positively affect the state of our planet. If we take the right actions not only could we stop the rise in green house gasses but we could also reverse them, making up for the increase in temperature of the sun, if it is in fact happening.

Could global warming be a good thing?

In Roman times it is said they used to grow grapes as far north as Northumberland. So some places may look set to benefit, however at the same time Libya used to be the bread basket of the Roman empire and global warming won't bring that back.

It is clear that the world has both warmed and cooled over time, but generally this has happened fairly slowly. What we have here seems to me to be far too rapid. Mankind will definitely survive, but much could be lost, including a lot of people. Also the hunt to secure resources could end up in many expensive wars.

Lastly, the thing about global warming is that there will always be evidence pointing one way or another, and theories to explain how it is or is not happening. If we wanted to be rigorous we would arrange some sort of control experiment. Unfortunately we only have the one planet on which to do it. We therefor have to look at the balance of probabilities. We are only going to get one chance to get it right. More importantly fossil fuels are a finite resource, so we may as well develop the technologies to live without cheap fossil fuels now.

I will write an article on green taxes another day.


Anonymous said...

On the "no warming in the SH": Unfortunately, you have to be wary of skeptics who deliberately cherry pick data in order to fit a pre-conceived agenda. In this case the graph is of satellite data only. More comprehensive temperature records are kept [eg by the climate research unit at the University of East Anglia a graph of which you can see here] using data from as many sources as possible. This makes the overall record more reliable.

In particular, satellite data is extremely difficult to analyse for climatic trends, because there are big problems with putting data together from different satellites, or in calibrating the instruments, and a host of other reasons.

As a scientist, I'd be embarassed to hold up that satellite timeseries as some sort of "disproof" to the records kept by CRU, etc. There hasn't even been an attempt to estimate the uncertainty!

Anyway, you can see from the CRU/Hadley plot that the SH is warming, although not as much as the NH. This is simply because more of the SH is ocean than the NH, and the oceans take longer to warm up than the land.

This is, when you think about it, a very obvious difference that follows simply from the different heat capacities of the oceans compared to land. This same difference is the reason why you get a coastal "sea breeze", and is also the reason why the climate of the British Isle is considerably milder than continental Europe. We are much more influenced by the Atlantic, which does not change temperature as much as the interior of the European continent.

I'd suggest that RealClimate would be a better place to keep up-to-date with recent climate research. It's written by climate scientists who put a fair bit of effort into explaining the science so that laypersons can understand it.

There is a lot that we don't yet know about global warming, but there is also a lot that has been established, and it is important not to get confused about what is knwon and what isn't.

On the sun: Even if the sun were getting hotter, it wouldn't stop higher CO2 levels from having a warming effect. The key question then would be what the balance between the two was. Research indicates that the warming 1910-1940 was mostly caused by a combination of the sun and a lack of volcanic activity [which normally cools the Earth]. Effects due to human pollutants were roughly balanced between cooling due to aerosols and heating due to CO2, etc. Since 1970, the effects of CO2 have far outweighed those from aerosols, and solar has been constant [as near as we can tell and certainly much less than CO2].

I concur with your point about rapid change. It is probably a very hard problem to define what an optimal world climate would be, but mostly you would have to say that it would be the climate we are already used to. Cities and agriculture are all based around the climate as it is [or was], and if you change where the rain falls you can have a problem.

A couple of further points that might be of interest. You mentioned the Sahara. I did hear of an interesting experiment that was done at the Hadley centre. They started their climate model with a "green Sahara", and the result was that the presence of vegetation in the Sahara affected the weather, making it rain, sustaining the vegetation. Once the vegetation is gone, the weather changes, and you're left with the harsh desert of today.

The same process can happen with the rainforests. Once they are cut down, their absence leads to less rainfall, which means they wouldn't grow back again.

There's a fancy mathematical name for this concept [hysteresis?], and a lot of the components of the climate system are subject to it - the Greenland ice cap is probably another example.

The key thing, as far as I am concerned, is about choices. The biggest uncertainty is still about how much CO2, etc we emit. If we manage to keep warming below 2C then we have a very good chance of avoiding the melt of the Greenland ice cap and the complete loss of Tibetan glaciers. Greenland is about 7m in terms of global sea level rise, and the Tibetan glaciers are relied on by hundreds of millions for irrigation.

A US climate researcher [Schlesinger?] said that reducing CO2 emissions was very similar to taking out an insurance policy, and the earlier we start taking action, the easier [cheaper] it will be. If you're willing to take insurance out on your home, why not your world?

Benedict White said...

Thank you for your comments Timothy.

On the southern hemisphere thing thing you are rigth about the water, but also there are less CO2 emmisions so it keeps it self in balence a bit better. Thank you for pointing out the lack of error margins in the article to which I referred, my main aim was to show that there could be contradictory evidence.

That said there are some new satalites meant to measure CO2 levels which do vary by region and season. The more research the better as far as I am concerned.

I did not mention the sahara, I mentioned Libya, that said in the 50's my father was in Sudan which I think borders the sahara and when they fenced bits of it off from grazing animals they became very green.

Your point about a green saharah crating its own rain is well made. I have known tis for a long time. We can generate a lot of green energy and other things in the deserts and bring about positive climate change as well. All it takes is the will to do it.

On the sun issue, I had thought I was clear in that I said even if the sun is warming that does not mean that CO2 levels are not important. Maybe I need to re write that part.

Thanks also for the links.

Lenoxus said...

Some of the most heartwarming words I read today were "stop laughing in the back" -- a reminder that are are countries (like yours) where the general public opinion meshes more of less with scientific consensus. Here in the States, hundreds of notable personages (in politics, the media, corporations, etc.) have done a brilliant job of making it look like the odds are nearly 50-50 that AGW is the case, merely because there are two sides to the issue (and besides, even the most rigorously considered model is still "just an opinion," right?). Then again, similar debates occur with regards to whether or not intelligent design is a kind of science, (Darwinism is "only a theory," I'm sure you've heard that one before) so go figure...

At this point, I'm completely tired of debates whereby the mere existence of evidence to the contrary (evidence suggesting that the earth isn't really warming, or the warmign isn't really caused be humans) is supposed to render all climatological opinions irrelevant -- unnecessary postmodernism if you ask me. Suffice to say that here, "conservatism" still means "unquestioning opposition to environmental science, and possibly even the idea of science itself." Hence, screaming contests erupt in which both sides become narrowly ideological, and "mainstream" Americans are left apathetic, thinking that "global wamring" is just hysteria, and do nothing at all, which of course is the worse place we can be without deliberately adding even more CO2 t the atmosphere. Seeing the conversation between you and Timothy is almost surreal in its sophistication, but I'm loving it for that.

So, major kudos for your well-thought out stance and examination the pros and cons of each side.

Lenoxus said...

whoops, that should be "more or less," not "more of less" and "warming" not "warmign."

Benedict White said...

Lenoxus, Thanks very much for your kind words, I am pleased that you liked the article and discussion that went with it.

Why not try emailing it to a friend ;)

What i hoped to achieve was showing that in such a debate as global warming there will be, and in fact have to be doubts but that does not mean we should not take the threat seriously.

We also need to do much more research.

I note you mention of Darwinism, I see it like this. Newons laws of motion were laws rather than just theories because you could prove or disprove them. We now know they are wrng, but only at high speeds or very large masses. Darwinism and creationism deal with something that is not susceptable to rigourous proof so mut remain theories.

What I can't understand about the literal creationists though is tahtthey seem to think they know how long God's days are. What ever happened to God moving in mysterious ways etc. They also seem to assume that the Word of God as expressed in the Bible is meant to be a scientific treatease. However if you take the seven day creatin story, and remove the need for God's days to be our own or indeed linear in our understanding then the order seems about right which is remarkable indeed considering how old the story is. But that is another discussion all to gether.

On the Conservative thing, the first responsibility of a Conservative government is to be competent. The USA therefore does not have a Conservative government.