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Mumbai to Katrina: Blame it on yourself?
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September 06, 2005

Floods in Europe, Pakistan, Maharashtra, Gujarat, typhoons in China, hurricanes in America: doomsday prophets perhaps never had it so good. But for a while now, scientists have been pointing at climate change as the reason for nature changing her ways.

Every once in a while, out pops a study that rings another alarm bell for another part of the world. Like the Potsdam Institute For Climate Impact Reasearch's recent study that said 'increasing air pollution and forest conversion in South Asia could lead to a failure of the Indian monsoon.'

Two factors, says the study, can make the monsoon behave in eerie ways. One of them is aerosol: the scientific name for airborne particles caused by burning fossil fuels. The other factor is greenhouse gases: carbon dioxide, methane etc, which increase the earth's temperature and lead to disastrous amounts of rain.

Also see: Water's Wrath, from Mumbai to Mississippi

To clear the air, rediff India Abroad Senior Features Editor Sumit Bhattacharya spoke to Dr Kirsten Zickfeld, one of the invesigators in the study, over the phone from Germany [Images]. She said while it is too early to pinpoint what caused Mumbai's Terrible Tuesday, there are enough signs to show that man's interference could cause the monsoon to wreak havoc.

First of all, why did you choose to undertake a study on the Indian monsoon?

We were looking at climate phenomena around the world that exhibit some kind of non-linear behaviour and the monsoon is one. This kind of phenomena are prone to some kind of threshold behaviour: when you exceed the threshold, rather dramatic things happen.

Another example would be the Gulf Stream or the thermohaline circulation in the Atlantic (which has a big impact on global climate)as we call it.

Did you get the cue from or refer to any previous studies?

We have a climate department here at PIK (the Potsdam Institute) that is headed by Martin Claussen. He is one of the guys who pioneered studies in climate-vegetation interactions. For example they looked at the African monsoon and at the interaction of the monsoon there and the vegetation. We drew on this study about the African monsoon to develop our model of the Indian monsoon.

Was your study done entirely from Germany?

It is a very theoretical project. It's a sort of mathematical model which was rather simple. Our observational data was taken entirely from available books, studies and research data.

Would you say your study is an alarm bell for India?

What we showed was there is this possibility of failure of the Indian monsoon because of anthropogenic interferences: like emissions of particles because of forest clearance. We cannot really access the probability of this failure because we do not know how many aerosols will be emitted in the future. We do not know how land cover will change in South Asia in the next decade or so.

There is a need to do some sort of study to really explore the scenario: to assess what emissions will be in future, how land use will change then take more and more complex models and run this scenario. That would allow one to make some statement about the probability of the monsoon.

The study says the monsoon is in danger, but we have had floods in the western states of Gujarat and Maharashtra. Are you aware of that?

Of course, we are aware of this.

How do you explain that in the context of your study?

First of all we don't make any kind of prediction. We don't say, 'This is going to happen.' We say, 'This is a possibility.'

On top of air pollution you have increasing concentration of greenhouse gases. This means you increase carbon dioxide, methane and all this kind of gases in the atmosphere. This is called global warming, and it has the opposite effect on the monsoon in India.

If greenhouse gases increase then the monsoon also increases.

So there are two competing effects: on one hand it's weakening because of the aerosols on the other hand it's strengthening because of greenhouse gases. We are not in a position to say which one of these effects will dominate.

How drastically does the monsoon reduce when you cross the threshold?

It reduces very drastically. If the average rainfall from June to August is something like 8 mm per day all over India, it would go down to 1 mm per day if the threshold is crossed.

What would be your advice to Indian policy makers?

I would say every time humankind interferes with the environment, it can disrupt some kind of climate phenomenon. I would say try to control aerosol emissions, I would say try to control greenhouse gases. I would say formulate policy to reduce emissions of aerosols, stop cutting off forestland.

The march of development versus ecological balance has always been a gray area. How critical is the pollution's effect on the monsoon now?

that is more environment-friendly) you need some time.

So I would say that if you really want to be on the safe side then one would have to start now to implement some kind of policy.

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