Introduction To Climate Change
What is this problem called climate change or global warming and how will it affect us, the whales and the dolphins?
Light and warmth on planet Earth comes almost exclusively from the sun. What happens to this arriving solar radiation - including how much of it is bounced back into space - depends on a number of things, including the composition of gases in the atmosphere and how reflective the Earths surface is (for example, polar ice is more reflective than ploughed fields).
Most importantly it is our planets atmosphere that has moderated the effects of solar radiation to maintain the conditions that we now enjoy, and which has also allowed life on earth to evolve and be maintained here for many millions of years. The greenhouse effect is a natural phenomenon caused by the atmosphere and which helps to keep Earth warm. (You might think of the atmosphere as a blanket around the Earth, keeping a lot of the heat in). However, in the last centuries we have significantly changed the atmosphere, putting extra amounts of what have become known as greenhouse gases into it. (The blanket has become thicker and the temperature underneath is becoming dangerously hot.)
The main greenhouse gas being pumped out by humankind is carbon dioxide and it comes from the burning of fossil fuels (oil and gas) which we use to power our factories, warm and light our homes and run our cars. The increasing amounts of greenhouse gases mean the atmosphere is retaining more heat and so it is that the planet is warming up. At the same time this increased warmth is melting the polar ice cover - so there is less shiny ice to reflect light away and this too is increasing the warming effect. In addition vast areas of rain forest are being destroyed and this is releasing carbon dioxide into the atmosphere.
Concerns about this situation have existed for some time and several years ago world governments set up a body of scientists from all over the world, known as the Intergovermental Panel on Climate Change (IPCC) to advise them. The IPCC has been monitoring the temperature and atmosphere and using sophisticated computer models to predict what will happen next. The panel has produced a number of reports which have explained what we know and what is likely to happen next. They published their fourth and latest assessment in 2007. This says that the earths average temperature has risen by 0.74 degrees in the period from 1906 to 2005, and that the average temperature will continue to rise.
This temperature rise may not sound like a lot, but it is in terms of the impact it has! It is not evenly distributed across the planet. The warming effect is stronger over land areas than over the sea, and accordingly it is strongest in the northern hemisphere where there is more land. At the same time as temperature has increased, sea-level has risen, occurrences of violent storms and heat waves have also increased, and the ice at the worlds poles and on its mountains is increasingly melting. These are all phenomena predicted to occur in association with global warming and it seems they are already happening. Also according to the most recent IPCC report, eleven of the last twelve years (1995-2006) rank in the twelve warmest years since 1850 when record keeping began. Since 1978, annual average Arctic sea extent has diminished by 2.7% per decade (with a decrease in summer ice of 7.4% per decade). It is possible that Arctic late-summer sea ice may disappear altogether by the last half of this century.
Melting Arctic ice has directed public attention to the situation of the polar bear for which the ice surface is an important habitat. Loss of polar ice threatens it and also those other marine mammals which live in association with the edge and underneath of the ice. These include the bowhead whales, belugas and narwhals. Changes in ice condition are likely to be very bad news for them.