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Predicting Climate Change

With these kinds of tiny things you can contribute a lot.


Our work helps modelling approaches or modellers that actually try to understand how current climate change is going to affect our society in the near future, or does already affect us.  For example, when we look to paleoclimate records, and it’s very well dated, we pretty much know when things happened, you can go into statistics and look at how frequent are certain extreme events, it may be a flooding, it may be a drought, it may be all kind of funny things, and then we can actually reconstruct…OK, in the past, under just natural conditions, the likelihood for such extreme events was such and such.  And then, if we add for the last 100 years or so of human activity, or the last 50 maybe only, human impact, then we can maybe see an increase in such extreme excursions and then you wonder ‘Hmm, maybe these two are linked’.  Of course, that’s not a bullet point, it’s not the smoking gun to pin point it, but it’s very strong evidence for such links and then of course we have to go to the modelling side again and try to understand what are the physical meanings, what are the reasons for such links, would that actually be feasible?


In one study we published earlier this year in Nature Geoscience, colleagues and me found in a stalagmite actual evidence for changes in aerosol loads, and that aerosols can change the circulation pattern over the North Atlantic or northern hemisphere and this changes also the rainfall pattern, so the input of human aerosols from burning gasoline or just industry changes circulation pattern, it has an impact on rainfall variability, and rainfall of course is extremely important if you're a farmer somewhere, and so there is quite clear information from our side that people that work with models and supercomputers, they can use that information to use their models, to test their models, how good are these models. So our data is a baseline, basically, we can compare if their models give the same answer if they compare it to our data for the last 50 or 100 years or so, and if they do that they can understand the fidelity of this model, how well does it actually represent the natural conditions.  If it confirms what we found before we say, well then, that’s a robust model, let’s go into the future and extrapolate the next 100 years or ten years or five years and see what it does: that’s what we also did in our study.  If it does not confirm what we found in our study then something in the model is wrong, so there’s clearly some parameter that has to be adjusted and has to be understood better before the model can be used to make any kind of forecasts for the future.


So if you make forecasts, there are different ways of doing that: if you look at the Met Office, they give forecasts maybe four, five days and you know from your evening TV how good or bad your forecasts is for…is it going to rain tomorrow or not.  Tomorrow may be quite OK, but then go to the weekend, next weekend, then it’s maybe like 50:50 it’s going to rain or not.  If you look at models that look into the next ten years, fifteen years, you can imagine how complicated this is.  So it’s comparable to people trying to forecast earthquakes, you look into the past and see that earthquakes happen every 120 years, so the next one is overdue.  But it could be tomorrow, it could be another 200 years , it’s unpredictable really.  In paleoclimate we are a little better off, at least simply because of statistics, but it’s still very, very difficult and in the Chinese paper that we just published we try such forecasts and a look forward, but there are large uncertainties with this.  We could never say there will be a huge drought in  2021 or something, we can just look at the likelihood and just say the probability that something is going to change increases, and we will probably see more drought events, but at the same time we can also find more flood events and this is not necessarily contradictory because if you look at the monsoonal system, it’s a very, very sensitive system and it’s very seasonal. So the summer monsoon comes in June and it lasts until September, maybe October, and then it’s gone again.


Now if you change this, the total annual amount of rainfall must not necessarily change, it could be always the same amount, but the distribution in the season is different, so you could actually imagine the monsoon starts maybe two weeks later, but then all in a deluge you get all the water of the year in two months and then the wet season is over and the dry season kicks in and then the dry season is longer and also drier, and of course such high frequency variability is very bad for farmers. The farmers in India, in Indonesia, in China, they depend on the timely arrival of the rainfall and timely means by the week, so they actually really depend on the next week’s rainfall.  If that does not happen, if the rain comes late, then they will have trouble.  If at the same time the rain comes too early, everything is starting to rot.  If the rain does not abate in the autumn, then it is also bad because things start to rot.  Last year we went to Belize and talked to Maya local people that we work with, they had exactly this trouble, they told us, they said it’s already November and it’s still raining and it shouldn’t, all of our cocoa and rice and things is going to rot in the fields and we can’t do anything about it.  So there is a very delicate balance between drought and flood and seasonality, and we know from multiple studies by now that things are going to change.


On people’s responses to climate

When we look at past and modern society, in the past everybody that was working was a farmer, and that was before industrialisation kicked in, people were extremely dependent on grain yields or agricultural output. Also, transport means were quite different, so if there was a drought in some region, it was very, very difficult to bring any goods there and to help them, while in a different region everything might have been normal.  If you look at the Tambora eruption in 1915, which then led to a a year without summer in Europe, and also in America partly, there were regions that just saw a huge increase in rainfall, Belgium for example, these regions would have no output from the fields, the grapes wouldn't ripen etc. But they still got some help from outdoors because…for example, Russia at that time yields were pretty much normal and there was not such a big problem, and the Tsar helped Europe by reporting more grain, so that’s alright.  But then in China, if you go several hundred years back, there would not have been any way to transport over hundreds of kilometres all the grain you need for feeding the people.  And then, if you look at the industrial civilisation today, I think we are spoiled, we can just transport anything to anywhere, you get your meat from Australia or from New Zealand and you carry organic stuff all over the place in a very speedy way, and that’s dangerous because we are still vulnerable.  


To some degree, we lost our link to nature and we thought, OK, with engineering you can do anything, but that’s of course not true.  Just look at the huge drought in California, it’s now in the fifth or sixth year or so, and people start to worry, they worry very late actually, and if you look at this extremely industrialised region where people have all the means of super computers to look more into the system and understand the climate there, it does not help to bring them more water, the only thing you can do, you can drill deeper wells, if you are rich you can drill deeper, but at some point your ground water is gone, and that’s what people do at the moment, they pump it out, and that water is maybe 10,000 years old.  And you actually can see that the ground is lowering because they're pumping out so much water.  And that’s of course leading to other problems, not just directly from the drought but indirectly.  Costs are just enormous.  If the drought lasts another couple of years then people have to move, they will not be able to sustain this for very long, and in America maybe kind of less critical than comparably to India or China where people have no such means or very little. 


On educating people about climate

I think that on the whole people are quite aware, at least in Europe, they are quite aware that such changes are ongoing, it’s also due to different teaching in school and a different information policy in Europe. In America things are different because there’s all this climate sceptics business, but I think here its quite OK.  And again, policy makers are probably briefed quite well, they have scientific advisers, but sometimes you feel like they should actually start doing something.  I have the feeling that politicians actually react, but they react very, very slowly because it costs money, it’s not a popular thing you have to do and it’s also not easy to actually pinpoint exactly what do you have to do to make things better.  But sometimes you would really like to see a bit more action and a bit less bubbling.  For every person out there who is not a policy maker, and that’s the majority of us, we can still do it with small things, everybody can contribute.  Switch your light off, switch your computer off when you go to bed, don’t leave it on standby, you use a hell of a lot of energy for nothing really.  With these kinds of tiny things you can contribute a lot, if everybody would do that we would save quite a lot of energy, and this is something people are not so much aware of. People that are thinking about the environment all the time anyway, they know that, but not necessarily my parents or everybody out there that is really ignorant of such things. 


- Dr Sebastian Breitenbach