By Donella Meadows

–February 16, 1995–

“Is the Earth Really Getting Warmer?” asked a recent Reader’s Digest article and concluded no, it is not.  A few weeks later came a New York Times headline: “Global Warming Resumed in 1994.”

“Give us a break!” I can hear people groaning.  “Would the experts please go fight this out over in a corner and stop bothering us until they figure out what’s going on?”

That’s an understandable reaction, but an impractical one. By the time the last scientist is convinced (he or she will work for a coal company), global warming will be far advanced.  Climate change takes decades to become apparent and probably centuries to reverse. To spot it in time to avoid it, we need to look for early warning signals.

So I keep a folder labeled “Global Warming Evidence,” into which I drop clippings.  It’s getting disturbingly thick.

For example, the New York Times piece said 1994 was the third or fourth warmest year since 1880, when reliable surface temperature measurements began.  (The warmest year was 1990 — 1994 tied with 1987 for third/fourth.)  That means the “Pinatubo cooling,” which began in 1991 with the eruption of the Philippine volcano Pinatubo, is over.  The dust has literally settled.

The Reader’s Digest article did not pick up a warming trend because it relied on satellite data beginning in 1979.  Fifteen years is not long enough to show climate change, especially since the last few years were biased downward by Pinatubo.

Thomas Goreau of the Global Coral Reef Alliance tells me he saw the arrival and departure of the Pinatubo cooling in the oceans.  Coral turn white if the algae that live cooperatively within them suddenly leave — which happens if there’s a rise of a degree or two in water temperature.  If the algae stay away long enough, the coral die.  In the 1980s coral were bleaching all over the tropics.  During the Pinatubo cooling, they colored up again.  Last summer the bleaching re-appeared.

The February 5 Science contains a report by ecologists who found in Monterey Bay, California, some brass bolts left in the seabed by a biological team that did a survey in the 1930s of the snails, barnacles, anemones, and other forms of sea life.  Because of the bolts, the study could be repeated in the same place 60 years later.  It revealed great changes in the bay’s inhabitants. Species that normally occupy a more southern range have greatly increased. Cool-water species have declined.  The whole marine community seems to have shifted northward.

Northward shifts have also been documented at a field station in Michigan that has been recording wildlife populations for over 80 years.  The deer mouse, the grayling fish and the calypso orchid have left for Canada.  Southern species, such as the ebony spleenwort fern and the orange-spotted sunfish, have appeared.  Throughout the United States armadillos, opossums, mockingbirds, and cardinals are moving north.

David Norton of Barrow, Alaska, tells me that willows growing along Alaskan rivers are advancing north.  At the opposite pole, just two kinds of flowering plants can survive the harsh Antarctic climate, and both of them are spreading.  Average summer temperature in Antarctica has gone up by almost 4 degrees Fahrenheit.  The growing season has lengthened by two weeks.

In Tasmania tree rings show that 700-year-old pines have been growing with uncharacteristic speed since around 1965.  Tree rings from Canada and Alaska indicate a gradual warming since 1840.

In the U.S. Midwest average temperature has gone up and average precipitation down over the past 95 years.  Lake Mendota in Wisconsin now thaws in spring an average of 12 days sooner than it did between 1900 and 1979.  Winter snow cover in the northern hemisphere has been receding since 1972.  Glaciers are shrinking all over the planet, many at rates exceeding 30 feet per year.

Average water temperature at Toolik Lake, Alaska, has gone up more than 3 degrees F. in the past 15 years.  The surrounding tundra is beginning to thaw, dry out, and oxidize to carbon dioxide — and that is the scariest piece of evidence in my folder.  Tundra is normally a carbon sink.  Mosses and other plants grow in the Arctic summer, absorb carbon dioxide, then freeze, entombing the carbon in layer after layer of permafrost.  If warming starts to reverse that process, we get a vicious circle.  The tundra releases carbon dioxide, which is a greenhouse gas that creates still more warming, more thawing, more carbon release, and so forth.  To give you an idea of the possible size of this runaway process, human fossil fuel burning releases into the atmosphere about 5 billion tons of carbon per year.  There are 180 billion tons of carbon stored in Arctic soils.

Another piece of evidence caused a sensation in December at an American Geophysical Union meeting.  Engineer David J. Thompson of Bell Labs found a way of reading a new signal from 300-year temperature records from England and other places where measurements go back that far.  The signal, related to the timing of the onset of each season, began to look strange about the middle of the 20th century.  “Changes in carbon dioxide resulting from human activities are causing large and readily observable changes both in the average temperature and in the seasonal cycle,” Thompson said.

People who, for financial or ideological reasons, do not want to believe in global warming will point out, correctly, that none of this evidence proves a global warming.  Cautious scientists, will say there is no doubt that greenhouse gases are increasing in the atmosphere, that those gases trap heat, and that a warming is probable, but it is still hard to see in the normal noisy variations of the weather.  Then there are people in touch with the planet’s living systems and leading indicators, to whom it seems that the earth could hardly be sending a clearer signal if it were jumping up and down and yelling, “Hey, I’m changing!”

Copyright Sustainability Institute 1995