VOA标准英语2011--Many Unknowns about Future Climate Change Effects（在线收听）

Many Unknowns about Future Climate Change Effects

Scientists say many of the long-term effects of rising temperatures are still unknown. They’re discussing the problem at the U.N. climate change conference in Durban, South Africa. Researchers say climate change is a complex mix of potential benefits and consequences, especially regarding food production.

In early November, researchers from several countries met in Beijing. They represented the so-called BRICS countries – Brazil, Russia, India, China and South Africa – as well as the United States and Indonesia. They discussed climate change and food security and agreed on a number of issues and recommendations to present to the Durban conference.

One of those researchers – Gerald Nelson – said they came up with a work program for climate change treaty negotiators. It concentrates on the role of agriculture.

“The advantage of the work program is that it puts these research findings about the importance of looking at climate change effects on agriculture – and also agriculture’s role in mitigation – directly into the record for delegates to look at,” he said.

We know we don’t know

Nelson is a senior fellow at IFPRI, the Washington-based International Food Policy Research Institute.

The ancient Greek philosopher Socrates is quoted as saying, “I know that I don’t know.” Nelson said it’s not that researchers don’t know anything about climate change, it’s just that they need to know a lot more.

"Our research results, our understanding of what’s going on on the surface of the planet today, is really hindered by a lack of data. We just have very little information about the actual changes that are taking place on the planet. We are still groping, perhaps not in the complete dark, but with only very limited illumination, to understand those changes. And we need to do a much better job of collecting data about where things are changing and how they’re changing,” he said.

Good and bad

At first glance, some of the changes being seen appear to be beneficial, at least for now.

“Take for example, in Iowa, farmers there are seeing longer growing seasons. They’re planting earlier in the year. They’re seeing wetter springs, with more summer precipitation happening. If you take a look at China, you see that Heilongjiang Province, which used to have essentially no rice production, now accounts for 15 percent of China’s rice production. In the northern parts of Russia, you’re finding grain growing that was not possible to grow there 20 or 30 years ago,” he said.

But what if global temperatures continue to rise? Would those apparent benefits continue? Maybe not.

“In the short run, they do seem to be positive,” said Nelson, “That is, rice production further north because it’s warmer potentially is a good thing for China. It’s harder to sort out the climate signals as you get towards the middle of the planet. It’s the northern extremes where you can see it earlier. But of course that’s with the climate change we have so far.”

Nelson says predictions call for substantially greater temperature increases. He says there’s been about a one degree Celsius rise over the past 100 years. But the forecast is for a two degree Celsius increase by 2050. Such an increase, he says, could have a dramatic effect on corn or maize.

“The corn plant, for example, can do ok as long as the temperature is in the range of 30 to 31 degrees Celsius. But as the temperature increases get above 30 or 31 to 32 or 33, recent research has shown substantial drop-off in yields,” he said.

Priorities

Nelson and others at the Beijing meeting came up with a list of 12 climate change priorities. One of them warns that a rise in temperature can also mean a rise in pests that attack crops.

“For insects, in particular, as the temperatures rise then they reproduce more rapidly. So, instead of having three cycles of a pest per season you might end up with four or five. And that means more damage to the plants as they grow,” he said.

And as temperatures rise, regions may lose killing frosts, which help limit insect populations. As for weeds, many are thriving in the richer CO2 or carbon dioxide environment.

Then there are ruminants, animals that produce lots of methane gas while digesting their food. Nelson says methane is much more powerful than CO2. More nations are expected to raise livestock for food as their lifestyles improve.

Other priority areas include soil ecosystems, irrigation, land use, biotechnology, food supply storage losses and training for researchers, farmers and others to better deal with climate change.