Scientists Seek Proof Positive of Global Warming Effects
On the American Agenda tonight: How do we know there really is a danger of global warming? As we were reported from Rio this evening, with or without U.S., Europe is going to put very strict limits on those gases that have the potential at least to trap heat in the Earth’s atmosphere like a greenhouse. The Bush administration is refusing to do so because, it says, the case for global warming is not compelling enough to demand that American industries use less oil and gas. We asked our Agenda reporter Ned Potter to explain what the evidence is.
These scientists are going diving to look for the greenhouse effect. Why look under water? Because this coral reef skirting the Florida Quays is normally darkened by algae. But the water here has become warmer than normal over the last decade forcing algae out and leaving some patches leech.
‘I think the cause of leeching is clearly a signal of greenhouse warming.’ This woman is a biologist with the World Wildlife Fund. ‘This is not a local thing, this is a global thing, regardless of whether corals are in proximity to the population centres, regardless of how they are managed. Everywhere in the world we are seeing some leeching.’
There is fairly little scientific debate over whether global warming is an issue, but there are many questions about how soon, how severely and in what ways we are most likely to feel it. So scientists are looking for what they call ‘greenhouse signals’, the first ecological changes that clearly can be linked to the warming.
The list of possibilities keeps growing. At the University of Delaware Dr. Young has used satellite data to track a giant warm spot in the waters of the South Pacific. It has grown warmer and larger over the last decade and Young says, it is probably a combination of regional weather patterns and greenhouse warming. At the University of Michigan biologists have been documenting several plant and animal species, as their habitats shift northward. One type of orchid which lives in hot weather could be found in this region 40 years ago, but has now retreated north almost a hundred miles. These species may be early warning indicators that tell us that natural ecosystems are beginning to respond to climate change.
They key phrase there is ‘may be’, because for every sign that suggests greenhouse warming there is another to cloud the picture. Clouds themselves are a question mark. In a greenhouse world more clouds would form, but would they shield us from the sun’s heat or trap more of it close to the Earth? Likewise, nobody can say how much additional heat the oceans would absorb or how much we can count on trees to absorb greenhouse gases. Even smoke from volcanoes, power stations and the burning of rainforests may act as a temporary sunshade.
That leaves a lot of room for some people to say: ‘Although we should be concerned with the issue, greenhouse warming is essentially non-problem for all practical purposes’, as Fred Singer, a scientist who often defends industries like coal and oil which are less concerned about the climate than about drastic economic measures being proposed to protect it. ‘Any time you try to limit the use of energy, you are really limiting economic growth.’
At Rio, the U.S. has been mindful of this argument trying to stop any agreement, it said, that would cost American jobs. Environmentalists say, that’s short-sighted, because a few prudent steps like energy efficiency can pay for themselves, even if global warming never happens.
‘People often wonder why should we do anything about the greenhouse effect until we are sure? Well, we’re not sure before we buy insurance to protect our health, we often make operations on our body when one doctor says do, and one says don’t. Why is it that environmental scientists should be 99 per cent sure?’
Many of them say, they may be sure within 10 years, but that meanwhile more and more industrial gases will get into the atmosphere, unlikely to dissipate for decades. That’s why researchers say, it is important to watch now for the satellite readings, and plant records, and dying corals. That may be telling us something.