Is The World Warming Up?

What is causing the warming ?

The United Nation’s Intergovernmental Panel on Climate Change ( the IPCC)conclude that human activity is very likely responsible ,by increasing the concentrations of greenhouses gases & the greenhouse effect .Over 25 scientific societies, including the national academies of science of the G8 nations,endorsed the conclusions.Some scientists ,how ever ,still disagree,arguing that the human contribution is minimal .

What is the greenhouse effect ?

The effect ,explains Robert Charlson , a professor at the University of Washington ,”has been on the scientific books for ever a century, it has been tested very thoroughly.” Certain gases cause the atmosphere to trap heat energy at the earth’s surface .Without the greenhouse effect,the earth’s average global temperature would be -18^o C, rather than the present comfortable 14,6 degrees.The concern is with the enhaced greenhouse effect that humans cause- that it will heat the planet too much.

What are greenhouse gases ?

The main greenhouse gases (GHGs) are carbon dioxide (CO² ), methane, nitrous oxide ,CCFCs ,and water vapour.Except CFCs , which have commercial purpose , the gases are found in nature .Burning fossil fuel, trees and agricultural waste adds to the CO² ,methane and nitrous oxide ,as do landfills, oil refineries and coal mines .And we affect water vapour indirectly.As the earth warms because other GHGs increase ,evaporation ramps up ,creating more water vapour.

How much have greenhouse gases increased?

“CO² has increased 35 per cent since the beginning of the industrial era,” says Gavin Schmidt, a climatologist with NASA’s Goddard Institute for Space Studies in New York.” Methane has more than doubled.Nitrous oxide has gone up 17 per cent .” Scientists are concerned about CO² because it is the abundant of the gases that we directly affect .While we have stabillised our CFCs and methane emissions , we have not the same with CO² so far.The carbon dioxide in the atmosphere continues to rise by about 0,4 per cent a year- because the fossil fuels that produce it fill 85 % of energy requirements.

Will CO² dissipate by itself ?

“No,” says NASA’s Schmidt..”It stays around for centuries, “ worldwide,we produce some 23,5 gigatonnes of CO² annually .(gigatonne is a trillion kilograms ) Fortunately ,only haft stays in the atmosphere and natural systems absorb the rest.

Oceans, our largest repository of carbon dioxide ,take in more than a quarter of our CO² emissions every year .The already hold about 50 times what is in the atmosphere and ten times what is in the land biosphere .But just how much more they can safely store is not clear .Ken Caldeira , a climate scientist with the Carnegie Institution of Washington , in Stanford , California ,says that in the oceans ,CO² becomes carbonic acid ,corrosive to the calcium carbonate skeletons of marine organisms .

Forests and plants soak up less than a quarter of CO² emissions.Through photosynthesis ,plans separate CO² into oxygen ,which they emit, and carbon ,which becomes part of their cells.David Ellsworth , a professor at the University of Western Sydney in Australia, is investigating how trees and plants will react to increased CO² by growing eucalyptus tress in chambers with evevated CO² levels.

What else besides greenhouse gases influences climate ?

Reguler shifts in the orbit of the earth and the tilt of the earth’s axis change how sunlight is distributed around the globe ,and may explain why the Ice Ages came and went .These shifts take place slowly over hundreds of thousands of years.

The total energy coming from the sun varies slightly .When the sun’s intensity is high, sunspots increase in number and the sun is brighter .But variations in the sun’s intensity haven’t produced the recent rise in temperature , say researchers at the Max Planck Institute for Solar System Research in Germany .in 2004 , they noted that while the earth’s temperature has risen dramatically in the last 30 years, solar brightness has not.

Tiny particles pumped into the atmosphere by erupting volcanoes and industrial pollution reflect some of the sun’s energy back to space , making things cooler.In 1991 .Mount Pinatubo in the Philippines blew so much dust the stratosphere that the temperature dropped by half a degree Celcius for two years.

Water vapour and clouds play a role ,but their impact is hard to predict .Water evaporating from warmer oceans creates clouds that can both trap heat and reflect it into space “low clouds tend to cool the planet .”Professor Charlson says “High clouds warm it .”

Feedback loops reinforce whatever is going on and are notoriously difficult to calculate .For example ,as the earth warms up,glaciers and sea ice melts.Then the surface of the earth becomes less reflective and warmer.This in turn melts more ice, causing more warming .

What’s convincing scientists that CO² is responsible for the recent warming ?

Many researchers have concluded that natural forces alone don’t explain the temperature increases over the last 30 or 40 years.Bruce Bauer .who studies ancient weather systems at the World Data Center for Paleoclimatology in Boulder, Colorado ,says,”When you try to do the math .the only way you can calculate the effects of artificial CO².”

The theory of heat- trapping gases projects that as CO² emissions go up,temperatures will rise in the lower atmosphere and at the surface of the earth .Thomas Karl , director of National Oceanic and Atmospheric Administration’s National Climate Data Center , says “The evidence continues to support a substarntial human impact on global temperatures increases.”

Richard Lindzen ,the Alfred P.Sloan Professor of Meteorology at Massachusetts Institute of Technology ,is uncovinced .”The effect (of human produced greenhouse gases ) is very small compared to normal changes that the climate is always undergoing.” He says .Lindzen attributes temperature increases over the past 100 years to”natural variability.” Can we predict this?.” So far ,no ,” he maintains .Will we be able to predict it in the future ?”Not much evidence of it.”

Stefan Rahmstorf, a professor of ocean physics at Potsdam Institurte for Climate Impact Research in Germany ,disagrees .In a February 2007 article in Science ,Rahmstorf points out that IPCC temperature projections are in line with current data .In 1990 the IPCC predicted that by 2006 ,tempetures would go up between 0.15 and 0.37 degrees.The actual increase was in this range – 0.33 degrees

HOW MUCH COULD TEMPERATURES RISE IN THE FUTURE ?

According to the IPCC, by 2100 , the average temperature might rise by as much as 5,8 ⁰C .But its report also states that we could hold temperature increases to a more bearable two degrees above pre-industrial levels.Getting that result means halving our current CO² emissions by 2050 , achievable if we lower them by slightly over one per cent of current levels every year until then