If nothing is done to combat the inexorable rise in greenhouse gases the resultant warming will have a pretty profound impact upon the climate. The IPCC estimates that by the end of this century global average temperatures could rise by 2.4 to 4.6 °C. The IPCC is an inherently conservative body it’s scientists are nominated by governments who also write the summaries which are the most read part of the reports. Any body which relies on consensus for its decision making is going to tend to the lower end of any scale to find agreement. Finally the closing date for research submissions was 2005 and given the requirement that all papers be peer reviewed and published the original research would have to have been conducted around 2003 or earlier. That’s almost 10 years ago. Given the rapid advances in the field of climate change research it is possible that the upper limit of temperature rises could be much higher. Indeed as the IPCC didn’t include some of the positive feedbacks in their calculations because no modelling existed for them some consider their estimates to be very low indeed especially towards the end of the century when the feedbacks begin to kick in with a vengeance. It should also be remembered that these are average temperatures, as the oceans are generally cooler temperatures over land will be higher. So for temperatures of 2.4 °C warmer that will mean on average 4 °C warmer over land and much warmer than that in the centre of continents and warmer still towards the poles.
Whilst these seem like relatively small numbers the change in global average temperature from the depths of the last ice age to today was only 5 °C. Although major fluctuations in global temperature have occurred before , the last few tens of thousands of years – the period precisely when human civilisation was developing has been characterised by a remarkably stable climate. Previous changes have also generally occurred over thousands of years allowing species to adapt to the changes. The warming caused by anthropogenic global warming will be in a matter of decades, many species already under severe stress from human induced habitat loss, pollution etc simply won’t survive. Indeed the IPCC estimate the extinction of 40 -70 % of the species currently in existence if temperatures exceed 3.5°C. That’s half of life on earth gone!!! That’s bad not just in of it’s self – some cute fluffy animals died – or more accurately cute scaly insects and plants but the fact that we are dependant on those self same species for the clean water we drink, the air we breathe etc. Much of agriculture depends on insects for the pollination of their crops. Although we have spent centuries in denial – in the west at least – humanity is part of nature, we are not above it, or in control of it. When it suffers so do we.
Melting ice and the thermal expansion of oceans (warmer water takes up more space) means rising sea levels the IPCC reckons half a meter by centuries end other scientists up to 2 meters and with either scenario much more to come – about 80 meters in total with all the water that is currently locked up in ice. Over 3 billion people live within 200 km of the coast, many of these will begin to feel the impact of greater storm surges. Millions in low lying river deltas such as in Bangladesh, the Mekong and the Nile will be forced from their homes. Low lying cities throughout the world are under threat rich and poor London, New York, Tokyo, Melbourne, Singapore, Saigon, Shanghai and Sydney. Warmer weather systems have more energy and are more dynamic which will lead to more extreme weather events , flooding ,storms and hurricanes will become more prevalent and more severe. Whilst it is impossible to link specific events to climate change there is no doubt that occurrences such as Hurricane Katrina and the recent floods in Pakistan and Queensland will become more commonplace.
However the most frightening consequence of climate change at least from a human perspective is the impact on food production. A warmer climate will lead to significant shifts in weather patterns, in particular rainfall will shift away from the mid latitudes and towards the poles. This will mean that the major grain producing areas such as the American Midwest, the Australian wheat belt and Central China will become much drier as will the dry tropical areas in Pakistan and India. The monsoon is likely to fail more regularly and the Himalayan glaciers which provide melt waters for irrigation for China, India, Bangladesh and Pakistan will disappear. Not only will there be less rain but higher temperatures also mean higher evaporation. Compounding this is that much of agriculture is close to it’s temperature threshold after which yields decrease dramatically. For example for rice most of the grains will be sterile if temperatures are higher then 36 °C for more than a few hours during the most crucial period in its development.
Some countries in northern latitudes will see increased yields due to a longer growing season and higher rainfall. Scientists predict that with temperature increases of up to 2°C this will balance out the decreases in other areas. However food shortages in poor (and not so poor) countries will still lead to significant regional conflict. With average temperature increases higher than 2°C there is likely to be a significant net reduction in the availability of food. Millions will starve. Africa will be the hardest hit of any continent, but the particularly scary thought is the consequence of food shortages in richer, more technologically advanced and potentially nuclear armed countries. If their populations are starving it is likely that Pakistan, Indian or China will resort to something a little bit stronger than concerts from ageing rockers to feed them.
It is almost certain that if we don’t do anything that a warmer world will mean an increasingly unpleasant existence for children being born today – if they survive at all. It will be a world characterised by mass extinctions, catastrophic natural disasters, floods of refugees and wars for scarce food, water and other resources. We have a chance to do something but the window of opportunity is very slim indeed. That’s why we have to act now – all of us – that means you too. The very future of your children indeed all future generations is dependant on you.