Salmon are known for swimming upstream. They're also known for surviving comfortably in very cold water -- after all, salmon live in pretty cold places. But as the earth's climate gets warmer, those icy waters are heating up, and their fish are suddenly finding themselves subjected to all kinds of bacteria to which they have no immunity.

The story's getting a lot of press right now, maybe because Alaskan fishermen are being forced to throw away as much as one third of their catch. Yet another reason for the skyrocketing prices of food worldwide.

But the story isn't new. For years, scientists have studied the effects of global warming on fish populations, and the current findings are right in line with much earlier reports.

According to a 2002 report summarized by the National Resources Defense Council, salmon and trout thrive in water that ranges from 50 to 65 degrees Fahrenheit, and in many locales, fish are living in streams at the upper end of that spectrum. This means that even a slight increase in temperature will render those waters uninhabitable.

The NRDC projects that by the year 2030, the streams in which salmon and trout live will increase by 0.7 to 1.4 degrees Fahrenheit. By 2060, they will increase by up to 3.2 degrees, and by 2090 -- or when my grandchildren will be middle-aged -- they will be almost five degrees warmer than they are now.

The upshot: By 2090, there may be a 38 percent decrease in salmon and trout from their current habitats if the carbon emissions threatening those areas are not reduced.

Obviously, this means the potential loss of a staple food for many Alaskans and a source of healthy protein for people everywhere. But it also means the decline of an enormous industry -- by some estimates, fisheries nationwide generate $14 billion -- and threatens the livlihoods of those who keep it going.

A 1992 report by D.A. Levy and published in the Canadian Technical Report of Fisheries and Aquactic Sciences found the following:

Global warming will increase water temperatures and decrease water flows during spawning migrations. Result: increased pre-spawning mortality. Salmon will die before reproducing.

Global warming will increase water temperatures during egg incubation. Result: salmon fry will emerge too early, increasing mortality.

Global warming will increase the severity and frequency of winter floods. Result: reduced survival rates of eggs to salmon "fry" or young juveniles.

Global warming will increase stream and river water temperatures. Result: conditions necessary for salmon survival will be less likely to occur.

Global warming will alter the timing and volume of stream flow discharges. Result: Reduced capability of streams to support juvenile salmon.

Global warming will alter conditions in Fraser river system lakes. Result: Lakes will be less suitable as nursery habitat for juvenile sockeye salmon.

Global warming, and resulting increased water temperatures, will alter the aquatic community as a whole. Result: adverse impacts on salmon populations.

Global warming will shift the timing of the spring freshet or snow melt into rivers and streams. Result: increased mortality of out-migrating juvenile salmon.

All this means one thing: We've known about the threat global warming poses to fish for decades, and now we're seeing that threat become a reality.