Human-induced climate change is likely to make many parts of the world uninhabitable, or at least uneconomic. Over the course of a few decades, if not sooner hundreds of millions of people may be compelled to relocate because of environmental pressures.
To a significant extent, water will be the most important determinant of these population movements. Dramatic alterations in the relation between water and society will be widespread, as emphasized in the new report from Working Group II of the Intergovernmental Panel on Climate Change. These shifts may include rising sea levels, stronger tropical cyclones, the loss of soil moisture under higher temperatures, more intense precipitation and flooding, more frequent droughts, the melting of glaciers and the changing seasonality of snowmelt.
Impacts will vary widely across the world. It will be important to keep our eye on at least four zones: low-lying coastal settlements, farm regions dependent on rivers fed by snowmelt and glacier melt, sub humid and arid regions, and humid areas in Southeast Asia vulnerable to changes in monsoon patterns. A significant rise in sea levels, even by a fraction of a meter could ruin tens or even hundreds of millions of people. One study found that although coastal areas less than 10 meters above sea level constitute only 2 percent of the world"s land, they contain 10 percent of its population. These coastal zones are vulnerable to storm surges and increased intensity of tropical cyclones—call it the New Orleans Effect.
Regions much farther inland will wither. Hundreds of millions of people, including many of the poorest farm households, live in river valleys where irrigation is fed by melting glaciers and snow. The annual snowmelt is coming earlier every year,
synchronizing
it less and less well with the summer growing season, and the glaciers are disappearing altogether. Thus, the vast numbers of farmers in the Indo-Gangetic Plain will most likely face severe disruptions in water availability.
Until now, the climate debate has focused on the basic science and the costs and benefits of reducing greenhouse gas emissions. Attention will now increasingly turn to the urgent challenge of adapting to the changes and helping those who are most affected. Some hard-hit places will be rescued by better infrastructure that protects against storm surges or economizes on water for agriculture. Others will shift successfully from agriculture to industry and services. Yet some places will be unable to adjust altogether, and suffering populations will most likely move. We are just beginning to understand these phenomena in quantitative terms. Economists, hydrologists, agronomists and climatologists will have to join forces to take the next steps in scientific understanding of this human crisis.
单选题
Which of the following is true according to the first two paragraphs?