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Greenhouse What we can The last decade is the warmest since reliable records were first kept over 130 years ago. Temperatures have been rising for the last century and sea levels have risen by 40-50cm since in global ternperatures in the 1980s... vay, a s . aN 4 “ C ; Pr a . he ‘greenhouse effect’ was a term first coined in 1896 by : = Swedish scientist Svante Arrhenius to describe the Scorch ers atmosphere’s warming mechanism. We now know it as the heating of the world due to human fuel consumption. The greenhouse effect is already happening. The questions Now the Us Midwest is in the grip of its worst drought in 50 years most people want answers to are ‘how far’ or ‘how fast’, but - destroying much of the US 1988 farm crop - and record high answering these is proving difficult. The US Environmental temperatures were set in over 70 US cities last June. Southern Protection Agency (EPA) reported in October 1988 that tempera- Europe, Turkey, the Middle East and China were hit by unprece- tures are expected to rise by 2° to 5° Celsius by the middle of the dented heatwaves last summer, with temperatures rising to over next century, melting ice caps and flooding coastal regions. The 40° for days at a time, and the Soviet Union was hit by its worst EPA draft report is the first major US assessment of greenhouse heatwave in 70 years. Moscow street bitumen turned to liquid effects; and peal bogs in surrounding farm districts erupted from sponta- “The ultimate effects will last for centuries and will be irre- neous combustion. versible,” the report said. The Midwest drought was cited before a June US Senate com- “If change is slow enough, nature can adap through migra- mittee - by the director of NASA's Institute for Space Studies, cli- tion and society can adjust. A rapid climate change, however, matologist Dr James E. Hansen - as evidence for greenhouse may overwhelm the ability of systems to adapt.” warming. He said that from 1780 to 1880, the earth’s average tem The EPA reported that at least 18,100 square kilometres in the perature warmed up by 0.9°C; from 1950 to 1980, the atmos- US alone will be inundated and up to 25% of crops in southern phere warmed by 0.6°; and the four warmest years in the last States will become too hot to farm. Hotter temperatures will century have fallen in the 1980s. increase smog and acid rain levels. “It’s time to stop waffling so much and say the evidence is As polar and glacial ice begins to melt, reflective ice is pretty strong that the greenhouse effect is here,” said Dr Hansen, replaced by heat-absorbing water, creating a feedback effect. To “There is only a one in 100 chance that this sequence could see what this can do we have only to look at maps showing the be a statistical fluke,” said Bill Genaro, a scientist from the US Na continental shelves off the Earth’s land masses - these roughly tional Weather Centre. correspond with the old coastline, which was inundated about “| don’t think anybody believes this is a once-in-50-years 12,000 years ago at the end of the last ice age. There’s much less phenomenon,” said Senator Patrick Leahy, chairperson of the US ice around these days - but since then the average temperature Senate agriculture Committee. of the biosphere rose by about 2° C. The atmosphere now has 25% more carbon dioxide (CO,) Many governments have instructed researchers to provide than it did before the Industrial Revolution. But when other predictions of sea level and temperature rises over a timespan of gases including methane, nitrous oxide and CFCs are included, one or two generations, Scientists have replied that they can only the concentration of greenhouse gases has increased by 40%. make rough projections for the next 5-10 years, not 25-50; but “Awarming of 1° would probably put the world warmer than they’ve been instructed to make longer-term projections any- any time in the last 120,000 years,” reported Dr Richard Warrick way. For this reason, most reports you see refer to major environ- of the US Climatic Research Unit. “If we followed the upper end mental changes occurring generations from now - changes of the estimates and heated the globe by 4°, well that is the which have already begun. difference between the depths of the last Ice Age and now.” 300 scientists from 48 countries who assembled in Toronto “The climate system is already changing and this is just the last June concluded that fossil fuel use must be cut by 20% by beginning,” said Dr David Rind, another NASA climatologist. the year 2000 and by 50% by 2015 if we are to slow and halt “The trend, clearly, is lo worse and worse droughts. The tempera- greenhouse warming. 2 NEXUS Ne mes Seven - Summer 1989 Now the Us Midwest is in the grip of its worst drought in 50 years - destroying much of the US 1988 farm crop - and record high temperatures were set in over 70 US cities last June. Southern Europe, Turkey, the Middle East and China were hit by unprece- dented heatwaves last summer, with temperatures rising to over 40° for days at a time, and the Soviet Union was hit by its worst heatwave in 70 years. Moscow street bitumen turned to liquid and peal bogs in surrounding farm districts erupted from sponta- neous combustion. The Midwest drought was cited before a June US Senate com- mittee - by the director of NASA’s Institute for Space Studies, cli- matologist Dr James E. Hansen - as evidence for greenhouse warming. He said that from 1780 to 1880, the earth’s average tem perature warmed up by 0.9°C; from 1950 to 1980, the atmos- phere warmed by 0.6°; and the four warmest years in the last century have fallen in the 1980s. “It’s time to stop waffling so much and say the evidence is preity strong that the greenhouse effect is here,” said Dr Hansen, “There is only a one in 100 chance that this sequence could be a statistical fluke,” said Bill Genaro, a scientist from the US Na tional Weather Centre. “1 don’t think anybody believes this is a once-in-50-years phenomenon,” said Senator Patrick Leahy, chairperson of the US Senate agriculture Committee. The atmosphere now has 25% more carbon dioxide (CO,) than it did before the Industrial Revolution. But when other gases including methane, nitrous oxide and CFCs are included, the concentration of greenhouse gases has increased by 40%. “Awarming of 1° would probably put the world warmer than any time in the last 120,000 years,” reported Dr Richard Warrick of the US Climatic Research Unit. “If we followed the upper end of the estimates and heated the globe by 4°, well that is the difference between the depths of the last Ice Age and now.” “The climate system is already changing and this is just the beginning,” said Dr David Rind, another NASA climatologist. “The trend, clearly, is lo worse and worse droughts. The tempera- hE Se