I SAW A colorful clothing advertisement on my way here. It said "global warming ready," and showed this city's famous San Marco square filled with parrots instead of pigeons. But if global warming proceeds at the current pace, the parrots of a newly tropical Europe will fly by overhead. For Venice could be well under water in future centuries.

Refugees fleeing the invasion of Germanic tribes in the 5th century could not have imagined when they first settled along this enchanted lagoon that their savior, the sea, could become their worst enemy.

Nowhere are the problems more obvious - the fragile lagoon against the background of chimneys spewing greenhouse gases on the mainland. It is not just a problem of industry lowering the water table that is causing Venice to sink. Rising sea levels worldwide will also have to be accounted for. Besides physical barriers to close the lagoon to floods, engineers here are seeking ways to help nature itself regenerate land.

It's not just coastal areas. Mountain countries are being impacted. Bhutan, which sells Himalayan hydropower for much of its national income, could see all of its 3,000 glaciers disappear within 50 years if warming trends continue at their current rate.

I came here for Mikhail Gorbachev's World Political Forum conference on how the press is handling global warming. The good news is that climate change coverage has increased in recent years faster than global temperatures. Al Gore's Nobel Prize and and his Academy Award-winning documentary, "An Inconvenient Truth," have had a huge impact. A book by America's foremost foreign affairs columnist, Thomas Friedman, on the necessity of going green is at the top of the best-seller list.

John McCain and Barack Obama both recognize climate change as a major problem, and even the Bush administration, so long in denial, has come at least partially around.

The bad news is that the problems grow faster than the public's perception. The search for alternative energy sources, still underfunded, is now more intense than ever. Debates on whether or not to allow wind farms rage on both sides of the Atlantic, from Nantucket Sound to the western isles of Scotland.

Until the recent financial crisis sucked all the ink and oxygen out of the airways, company after company was coming around to greener policies, linking up with the parallel need to get out of fossil-fuel dependency. That may no longer be a priority as the financial crisis deepens.

The irony for Europe is that climate change could result in colder, not warmer, temperatures. Northern Europe, on a parallel with Canada's Hudson Bay, enjoys its milder climate because of the Gulf Stream funneling heated water north. But in order to work, the Gulf Stream waters must be allowed to sink when they reach the cold waters of the north and make their way back south again along the ocean floor. Scientists at the Woods Hole Oceanographic Institution call this the "conveyor belt."

Should the waters from the Arctic become less cold, and less salty due to melting ice, as is now happening at a rapid rate, the Gulf Stream waters might not be able to sink as readily, thus breaking up the current, and bringing a colder climate to Northern Europe and North America. This has happened before. From the 16th century until the middle of the 19th century, Europe experienced markedly colder temperatures - as witnessed by paintings of people skating on the canals of Holland, which seldom happens today. And the famous painting of George Washington crossing the Delaware shows ice on the river at levels no longer seen.

The problem is all the more complicated in that man-made greenhouse gases are riding on the back of a normal warming trend following a 200-year cold snap.

It is easy to blame the messenger for not sufficiently alerting the public, but, as this conference has shown, there are so many interconnecting parts that make up the whole. And a solution in one sphere may create problems in another. Witness the surge of ethanol to solve a gasoline problem, only to cause food shortages. And, as the financial crisis shows, mankind seldom reacts before problems become too severe to ignore.

(By H.D.S. Greenway, Boston Globe, 14/10/2008)
H.D.S. Greenway's column appears regularly in the Globe.