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Global Warming Studies Improve
yoink! writes: "The BBC news service is running a story which indicates that previous global warming predictions failed to take the oceans and their temperatures into consideration. Those involved with the studies, according to the article, articulate our [homo sapiens'] important role in helping to warm earth's climate. This could very well add fuel to the debate between natural, polution independant, warming cycles and humanity's destruction of our only home."
Simply because the world's seawater stores millions of times more heat than the atmosphere, and the warm sea currents from tropical oceans transport some of this heat to northern continents like the USA and Europe which would otherwise be permanently freezing cold due to their northerly latitude. Warm sea currents are vital to agriculture and our continued well-being.
Yes, the warm sea currents that keep the planet warm have an Achilles heel -- sea currents stop moving if the saltiness of the seawater falls below a critical level (the density of seawater depends on its saltiness, reduced-salt seawater won't sink as it normally does in the coldest polar regions, and without sinking seawater the ocean currents stop moving).
One of the agreed effects of increasing Carbon Dioxide emissions is that rainfall will increase in northern latitudes, diluting the seawater. In the limit dilution shuts down the warm sea currents.
The Gulf Stream is the most important warm sea current because it can alter worldwide climate by various positive feedback mechanisms. The climate and food production of the USA and Europe, for example, both depend on the Gulf Stream keeping the climate warm enough to grow crops.
The Gulf Stream is known to be sensitive to changes in rainfall over the Atlantic. Rahmstorf's bifurcation model of Atlantic thermohaline circulation is widely accepted by independent scientists. This model implies the Atlantic Ocean has only two stable modes of circulation -- ON and OFF. The Atlantic Ocean is currently in the ON mode with an active Gulf Stream. 100000 years ago, it went into the OFF mode when the Gulf Stream shut down causing a worldwide massive Ice Age. The model shows the likely cause of the shutdown was increased rainfall.
The Gulf Stream changes slightly in intensity from year to year, but overall its average state in recent decades is stable and active. However, the situation should be monitored closely because it is unknown exactly how much additional rainfall the Gulf Stream can tolerate without shutting down. The Rahmstorf model predicts a critical threshold of about 1Sv/yr (10^6m/yr) (sustained increase) which is ~50% above current long-term average rainfall, whereas rainfall over Northern Europe has actually been increasing only by about 2% a year over the last 20 years -- a total rise of 40% which is currently below the 50% threshold. Conclusion: the Gulf Stream looks safe now but vulnerable to future rainfall increases.
Most agricultural plants probably wouldn't survive. The summer air temperature in the US Mid-West, for example, would be just 32F(0C) which would stop all agricultural production.
The ORNL has researched the types of vegetation in the US in present-day conditions and in zero-Gulf Stream conditions.
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