Monday, December 10, 2007

Gambling with the planet

On 10 Dec I gave a short talk to about 300 Italian sixteen to seventeen year olds from three or four schools in Rome. The talk was part of a debate about water management (itself part of a year-long project in which the schools had been working with members of the Italian national research councils and the national civil protection agency). My job was to contribute to an international perspective, especially with regard to climate change, and to encourage the kids to ask questions. The text from which I spoke (with simultaneous translation) is attached as a comment to this post.

1 comment:

Caspar Henderson said...

Ethics and polemics: Water – too much or too little?

Text for talk in Rome, 10 Dec 07.

I’m going to stand back from the question, and talk a little about probability and risk, starting with a very simple example. It will, I hope, become clear why this is relevant to what we’re here to talk about today.

I guess everyone knows what the probability is of getting heads, not tails, when I toss an unbiased coin. Anybody?

OK, who here can tell me what the probability is of getting heads, not tails, ten times in a row when I toss that same unbiased coin? [Answer: a bit less than one in a thousand]

Now here’s one that sounds difficult, but it may be some people here know the answer. What do many scientists believe to be the probability of avoiding a rise in the average global temperature of more than two degrees Centigrade if atmospheric concentrations of greenhouse gases are stabilized below 450ppm of carbon dioxide equivalent in the 21st century?

The answer is they think that, on current evidence, the odds are about fifty: fifty – the same as tossing a coin.

You may be thinking what has all this go to do with water?

I’m not going to try to answer that question right away. Instead, I’ll ask another question. Who here thinks they know why a 2 C rise in global average temperature is seen as a significant, and what that significance is?

After all, two degrees doesn't sound like much. If you go outside and it’s ten rather than eight degrees you might hardly notice, and if you do you might be glad that it’s warmer.

In fact, a rise in global average temperature 2 C is widely accepted – by scientists, national governments, the European Union and others – as the threshold for ‘dangerous climate change’.

It may seem strange. But consider this: the last time the global average temperature was 2 degrees hotter than it is today sea levels were many metres higher and hippopotamuses were living in London.

An average for the whole globe tells you very little about air temperature at a regional and local level – and the effects of those temperature changes.

The ‘dangerous climate change’ that the scientists are talking about includes:

• Increased water availability in moist tropics and high latitudes
• Decreasing water availability and increasing drought in mid latitudes and semi-arid low latitudes
• Hundreds of millions more people exposed to increased water stress
• (bleaching and death of many coral reefs, which support fisheries and provide other ecosystems services for hundreds of millions of people)

You will have noticed that the picture is quite complex – more water in some places, less in others. What it may mean for Italy is also complicated. Among other things, it’s not just what happens to the hydrological cycle in Italy that matters for Italians. For example, how would Italy manage many migrants and refugees from places experiences floods and droughts on a much greater scale?

The point is we’re starting from a situation that is already stressful. [we already know/we’ve already heard today] something about the pressures on water supplies. Let me add something to that.

I recently read that world water consumption has risen sixfold during the past century, more than double the rate of population growth. By 2025, almost two-thirds of the global population will live in countries where water will be a scarce commodity. Last week the United Nations secretary-general Ban Ki-moon warned that could lead to conflict.

[The head of the China’s national development agency said recently that a quarter of the length of China's seven main rivers was so poisoned that the water was harmful to the skin. Moreover, water-related issues are sparking popular protests after the sanctioning of dams and irrigation projects that have displaced hundreds of thousands of people who have no recourse to compensation.]

So even without climate change, demand for fresh, clean water is very likely to increase. But with climate change the challenges, and the risks are likely to be much bigger. And they would likely to start happening even before the global average temperature rose by as much up to 2 C.

OK, now for the bad news. Without radical and rapid changes in the way the world economy is powered, global average temperatures could well rise by more than 2 C in your lifetimes.

(I’m talking about within the next forty or fifty years. How old will you be in 2050? About sixty years old, right? Who here can imagine actually being sixty? Who here can think of someone who is sixty or older that they admire?)

The scientists stress that there still is a lot of uncertainty about the extent and the rate at which the earth system will respond to all the pollution we are adding. But they are getting more confident in their predictions. Two hundred leading researchers warned at the climate talks that began in Bali last week and continue this week that even by stablising atmospheric concentrations at 400 p.p.m. means we are only giving ourselves a three-quarter chance of guaranteeing a less than 2 °C rise.

Think about that. Those are significantly worse odds than a game of Russian roulette.

(Other leaders in the field have an even starker warning. Myles Allen and David Frame argue that it is probably a bad idea to assign a specific threshold value for CO2 concentrations in the atmosphere, above which "dangerous interference in the climate system" may result. For example, 450 ppm is an oft-cited threshold since this keeps deltaT below 2°C using standard climate sensitivities. But the skewed nature of the distribution of possible sensitivities means that it is much more likely that 450 ppm will give us more than 4.5°C of global warming rather than less than 2°...")

So what to do? To come up with a good answer will take months, years of work. But we have to start. A good place is to get to know the scale of the challenge.

World energy demand. In 2002 the world used 13.5TW (trillion Watts) or about 20,000 50 MW power plants. By 2050, with 3 billion extra people and greater energy demand, we will need between 28-35 TW (although it will be 45 at Euro rates of energy use or 102 at US rates).

Imagine that we tried to meet this demand entirely from renewable, carbon-free energy. We could dam all the remaining rivers. That gives 0.7 – 2 TW. Saturate the planet with windmills. That gives 2.1TW. Use all available land for biomass 7-10 TW. And we could uild a nuclear power station every two days for the next 45 years – 8 TW. If you do all of these the maximum feasible total is around 22.1 TW. But even with this we’re still a long way short of the 28 TW I mentioned as minimum demand.

A key part of solution is wiser use of energy and wiser use of water. We will talk a lot more about solutions today.

But the really important thing, I believe, is for us all to become active citizens.

You are young at the most exiting and the scariest time that one could be alive. You know in your hearts that your youth is the most tremendous gift. There is pain and fear ahead, to be sure, but there is so much to live for.

Many of you have grown up surrounded by great material comforts. But that time may end. Italy may be facing its greatest challenges since the collapse of the Roman Empire. (Why did the Roman Empire collapse?) It’s up to you to make this a Risorgimento

You will need to struggle and work hard and also to be patient. Listen to what the people who oppose you are saying. Try to understand their hopes and fears. They may seem very different, but if you truly listen you will discover that what you share is much more than what divides you. Never give in, never never, never given in.

Ignoring this problem is not a good idea. And it cannot be solved by buying more stuff.