Does greenhouse make sea bloom?

THIS summer's toxic algae bloom in the North Sea that cost fishermen several hundred million dollars in lost catches also gave a new perspective on climatic warming. Marine biologist Victor Smetacek of the Alfred Wegener Institute for Polar and Maritime Research in Bremerhaven, West Germany, says the air's rising enrichment with carbon dioxide (CO2) may be partly responsible for the abnormally lush algae growth.

CO2 - the most important of the climate-warming gases - is a plant nutrient. Algae, like all green plants, convert it into carbohydrates via photosynthesis. Thus air enriched in CO2, plus possible temperature changes related to climatic warming, could encourage such algae blooming.

This, of course, is speculation. But it does point up the fact that a rise of one to several degrees in our planet's average surface temperature is not the most important aspect of the greenhouse warming. The main impact is likely to appear in a variety of subtle ways that have major biological effects.

A team of NASA and Massachusetts Institute of Technology climate modelers emphasizes this in connection with a new global warming study it published in the Aug. 20 issue of the Journal of Geophysical Research. Led by James Hansen, director of NASA's Goddard Institute for Space Studies, the team has run new computer simulations of possible climatic effects of that warming over the next 70 years. These suggest, among other changes, that the probability of a hot summer is likely to rise above 50 percent in the 1990s, compared with about 33 percent in the past.

Commenting on such changes over such a short time span, the scientists say, ``We emphasize that it is the possibility of rapid climate change which is of most concern for the biosphere; there may not be sufficient time for many biosystems to adapt to the rapid changes forecast....''

This is a warning we should heed. Climate simulations like this are not definitive. The computations can't take account of all relevant factors. Yet they do provide useful insight.

Project Cohmap (Cooperative Holocene Mapping Project) at the University of Wisconsin's Center for Climatic Research is testing the ability of computer modeling to mimic past climate changes. In a major study covering the past 18,000 years published in the Aug. 26 issue of Science, the Cohmap team concludes that ``climate models have fair skill in simulating the broad geographic patterns of atmospheric circulation, temperature, and moisture.''

So, while simulations such as those run by Hansen and his colleagues may not be perfect, they do have credibility. They are good enough to put us on notice that, whatever specific climatic changes lie ahead, these will come fast enough to cause severe strain to the biosphere.

We have scarcely begun to suspect the many and often subtle ways in which this strain will appear. Lost crops and shifts of agricultural belts are only the most obvious of the possibilities.

In spite of the step-up in climatic research now under way, little work is being done on the possible ecological effects of climate change. Such work is badly needed.

A Tuesday column. Robert C. Cowen is the Monitor's natural science editor.