Kitabı oku: «How Can I Stop Climate Change: What is it and how to help», sayfa 4
four climate hotspots
Scientists have identified a number of hotspots around the world that could trigger fundamental changes in the global climate, including:
Amazon rainforest: Changes in the Sahara could reduce the fertility of the Amazon region, speeding up destruction of the rainforest.
North Atlantic ocean current: Melt-water from Arctic ice sheets could slow the North Atlantic ocean current, leading to cooling in northern Europe.
Asian monsoon: Changes to weather systems in the Atlantic could have a serious effect on the reliability of Asia’s annual rainfall.
Sahara desert: Dust from the Sahara fertilises the Amazon, but if the region gets wetter, there will be less soil erosion and more chance of plants returning to the Sahara.
Scientists are working to understand how such hotspots could affect the climate – and what impact climate change will have on the hotspots themselves.
The IPCC’s fourth report, issued in 2007, highlighted the growing evidence of observed climate change from around the world and looked at future predictions.
Its evidence is based on a consensus among the scientists involved. It is mainstream thinking – endorsed by international governments – and as such it can err on the side of caution. Some have suggested that the IPCC is in fact presenting a ‘bestcase scenario’, underplaying the evidence for more violent climate change. One author based at the Met Office Hadley Centre Richard Betts says that means that the result is ‘bullet proof’ in terms of the certainty of the science it contains. ‘When I read this [the IPCC report] for the first time I did feel fear – I had worked on it for three years and I knew it was right,’ he says.
what will the world be like with a changed climate?
Scientists can predict with increasing accuracy how the climate will respond to rising levels of pollution in the atmosphere. In 2007 the IPCC highlighted the scientific predictions about the impacts of climate change over the next 50 to 100 years, revealing a world in which billions of people will be at risk. Sub-Saharan Africa, large river delta areas in parts of Asia, small island states and the Arctic regions are likely to be particularly vulnerable.
“ It’s the poorest of the poor in the world, and this includes poor people even in prosperous societies, who are going to be the worst hit and who are the most vulnerable as far as the impacts of climate change are concerned.
Rajendra Pachauri, Chair of the IPCC
the Hadley Centre’s global climate models
The UK’s Met Office Hadley Centre is spearheading international research. Early climate models were simplistic replicas of the climate, covering temperature, rain and carbon dioxide, and were more useful for monitoring changes in the weather than for predicting future climate. Today’s models include a vast number of variables and have been shown to be capable of describing historical changes in the climate with reasonable accuracy. Interactive cloud systems, oceans, land-surface cover and aerosol pollution are all factored into the predictions made by models such as the Hadley Centre’s latest (global climate model) HadGEM1. This looks at 38 different layers of the atmosphere – allowing for greater accuracy in the predictions, and more regional detail than in older models.
Africa: Many countries are already becoming drier and this is predicted to get worse. Some 75-250 million people likely to face water shortages by 2020. Farm yields in some parts will be reduced by half by 2020. Greater risk of flooding near the Equator. Sea-level rise will affect some coastal areas by the end of the century. A quarter of Africa’s population lives in coastal areas.
Continental temperature trends
Asia: More than 1 billion people facing reduced supplies of fresh water in large river basins by mid-century. Deltas in China, India and Bangladesh at risk from rising seas. Salt water likely to contaminate the ground water. Floods may bring diseases like diarrhoea and cholera. Warming oceans will affect fish and fishing communities.
Europe: More flash floods and greater coastal erosion. In Southern Europe heat and less rainfall will be bad news for farming. Human health at risk from heat waves and smoke from wildfires. Drier summers in Central and Eastern Europe will put water supplies under stress. Forests and peat areas at risk from wildfires. In Northern Europe growing seasons likely to increase, and forest likely to flourish. Less need to heat homes but risk of more winter floods.
South America: Tropical rainforest in Eastern Amazonia likely to be dry grassland by mid-century. Species such as black spider monkeys, bearded sakis, red-handed tamarins, jaguar and pumas, will come under severe threat and some truly magnificent and significant species are likely to be lost for ever. Drier, and in some areas, saltier conditions could reduce food yields. Warmer conditions could boost soybean production in temperate areas. Vanishing glaciers will threaten water supplies in cities such as Lima, Peru, as well as hydroelectric power and farming.
North America: Farmers in northern regions could have longer growing seasons for a few decades. California may dry out and become more vulnerable to winter floods. Hotter weather and wildfires will pose health hazards. Parts of the eastern coast will see more intense hurricanes and tropical storms, storm surges and flooding.
Australia and New Zealand: Australia sees increasing water shortages by 2030 and significant loss of animal and plant varieties by 2020, particularly from the Great Barrier Reef and the Queensland Wet Tropics. Water shortages predicted for New Zealand’s North Island and rising temperatures will benefit farm yields for a time on the South Island. Risk of coastal flooding from mid-century in Australia and New Zealand.
UK climate change in the 21st century
Projected temperature increases, based on one of two IPCC scenarios – Low Emissions (+2.0°C, 525 ppm CO2 in 2080s) or High Emissions (+3.9°C, 810 ppm CO2 in 2080s)
climate change in the UK
With UK temperatures expected to increase by 2-3.5 °C by the 2080s, hot summers will be more frequent and very cold winters rare. Winter flooding is predicted to become more common, while farmers face shifts in growing seasons.
Sea levels will go on rising by 26-86 cm in the South East by 2080. Extreme high-water levels are likely to become more frequent, particularly on the east coast of England, and houses on floodplains are especially vulnerable. The Thames Barrier is likely to need replacing by 2030 if today’s levels of protection are to be maintained. Flooding is likely to hit the least well-off most: the most deprived 10 per cent of the population are eight times more likely to be living in the coastal floodplain than the wealthiest 10 per cent.
A study of UK wildlife found that eight species are under threat from climate change because of changes to habitat. Increased drought could mean fewer slugs and snails available as food for song thrushes in the south of England, with the population at risk across England, Wales and Ireland if warming continues. Skylarks, black grouse, common scoter and capercaillie are also likely to see their preferred habitat disappear. Stag beetles, currently only found in southern England, could find more suitable habitat further north. A warmer South East will attract new species: mosquitoes are already on the up and there are fears that malaria carriers could soon be in the UK. Some species will find they cannot adapt: the Snowdon lily could die out while the snow bunting is unlikely to be found in the UK.
the human cost
The human costs of inaction on climate change are incalculable. Millions of the world’s poorest people will experience dramatic changes in their way of life.
Regions close to the Equator – many of which rely on small-scale farming for food – will see bad harvests from a temperature rise of just 1-2°C. Farmers may be able to adapt by using different crop varieties and relying more on irrigation. But studies suggest that temperature increases above 3°C will be hard to accommodate. Heat will be bad news for dairy farmers: cows are less fertile, produce less milk and do not live as long in hot conditions. Cattle and pigs are also affected by heat – they tend to breed less.
Adapting to climate change will be difficult for small and family farms, for pastoralists and people who make a subsistence living on poor land, especially in parts of Africa and Asia. Without adaptation, crop yields are likely to fall and be badly affected by extreme weather events. Wealthy areas rich in resources are likely to adapt more easily.
Fishing communities will struggle as fish species migrate or die out. River fish will be affected as rainfall and snow melt patterns change. Millions of people, particularly in some of the poorest communities, rely on fishing to supplement their families’ diet.
Food will not be the only area of the economy that is damaged. The timber industry will see extreme weather and more wildfires, insects and pests.
Thousands – if not millions – of people have already left their homes because of the changing climate. The International Red Cross says 25 million people could already be classified as ‘environmental refugees’ in 2001 and it has been estimated that climate change could push the total number of displaced people worldwide to 1 billion by 2050. One study estimated that around 15 million were likely to be displaced from Bangladesh alone. In China 4,000 villages are likely to be abandoned as a result of the spread of the Gobi desert. Huge numbers of people on the move are thought likely to increase the risk of conflict in some areas where resources are most scarce.
health risks
The health of millions is at risk. The very young and very old will be most vulnerable. The IPCC warns of:
more malnutrition with long-term impacts for child growth and development
more deaths, disease and injury due to extreme weather events; people in urban areas will be most at risk – cities intensify temperatures because buildings hold heat
an increase in diseases, including diarrhoea and cholera as a result of water contamination caused by flooding
more problems such as chest infections and asthma because of increased low-level ozone
changes to the way infectious diseases spread.
The warming of colder regions will lead to fewer people dying of the cold. And changes to the climate could limit the spread of malaria in some parts of Africa. But over all, the health benefits of climate change are vastly outweighed by the negative effects, particularly in poorer areas.
Mortality and climate change Estimated deaths in 2000 attributed to climate change (compared to a 1961–1990 baseline) show that Sub-Saharan Africa and the rest of the developing world bear the health burden of climate change.
the cost to wildlife
Plants, birds and animals cannot easily adjust to rapid changes – either in temperatures or in their food supply. The potential toll on the wildlife-rich rainforest of the Amazon is an extreme example. Experts believe the golden toad and harlequin frog – both native to Costa Rica – have disappeared as a direct result of climate change. Animals as diverse as polar bears, tigers, penguins and pikas are at risk. Some 70 per cent of coral in the Indian Ocean has already died as a result of the heat.
The IPCC predicts that 20-30 per cent of plant and animal species are at an increased risk of being wiped off the face of the Earth if global average temperatures rise by more than 1.5-2.5°C. Indeed some scientists put climate change at the top of the list of threats to biodiversity in many regions.
JUMPING OFF POINT:
Scientist JA Pounds says Central American frog species have disappeared due to deadly infectious diseases spurred by global warming. ‘Disease is the bullet killing frogs, but climate change is pulling the trigger,’ he said.
In the UK long dry periods damage food supplies for migrating birds. Breeding redshanks, lapwings and snipe dropped by up to 80 per cent at five reserves in the south of England following the dry summer in 2005. And warmer seas are leading to fewer plankton off the British coast, with an impact on the sand eel population – resulting in less food for nesting birds like puffins.
As plants, insects, birds and animals migrate so the nature of our landscape will change. Traditional English woodland, populated with oak, beech and bluebells could become a thing of the past, as sycamore becomes the more dominant species and cow parsley could force snowdrops and bluebells out.
the economic cost
It’s easy to see the immediate costs of clearing up damage caused by floods, storms or warping railway tracks; less obviously, farmers across the world are paying the price in lost harvests, lower yields and higher prices. People who rely on rainforests for food, farming and forestry are losing their way of life.
In the developed world, the insurance industry generally picks up the tab for extreme weather. But in Europe the cost of flood damage alone would be expected to rise by up to £82 billion a year, and the costs of Hurricane Katrina have been put at US $125 billion. Many people in the poorest countries do not have insurance policies; but even in the rich developed world, many can’t afford insurance as the risk of extreme weather rises – particularly for those living in flood plains.
An economic assessment of the cost of climate change, commissioned by the UK Government and published in 2006, suggested that unchecked climate change could damage economic well-being worldwide by at least 5 per cent and by as much as 20 per cent. In other words a fifth of the world economy is at risk.
‘The impacts of climate change are not evenly distributed – the poorest countries and people will suffer earliest and most.’ The Stern Review, October 2006
how different temperature rises could affect us
The IPCC predicts temperature increases of 1.8-6.4 °C this century, depending on the amount of fossil fuel used. Its best estimate is 4 °C. While rises at the lower end of this spectrum would have terrible impacts for millions of people around the world, a rise of more than 6 °C could spell shocking global consequences.
HOT TIP:
A future with extreme climate change? Don’t go there. Experiments in South Africa’s Succulent Karoo desert show that a 4-6 °C rise in daytime temperature kills three quarters of plant species.
the six-degree scenario
Evidence suggests that the end-Permian extinction, 251 million years ago, may have been triggered by a rise of temperatures of 6 °C: it almost wiped out life on Earth. Forests, swamps and savannahs were washed away, land turned to desert; the warming oceans, which lose oxygen as temperatures rise, would have become stagnant and toxic. Some scientists believe the warming of the ocean would have been enough to trigger the release of huge clouds of methane from the sea bed, poisoning the atmosphere. Life on Earth did survive 6 °C of warming, but those changes took place over 10,000 years. Human releases of carbon dioxide are almost certainly happening faster than any natural releases since the beginning of life on Earth.
Writer Mark Lynas has studied historical records to examine the potential effects of temperature rises of up to 6 °C. Here is a summary of his six-degree scenario:
+1 °C: Deserts spread across parts of the United States, turning farmland to dust from Canada in the north to Texas in the south. The Gulf Stream could switch off – plunging Europe into an icy winter. Coral reefs around the world are wiped out.
+ 2 °C: Oceans turn increasingly acidic, killing off plankton and affecting sea life. European summers are plagued by heat waves as strong as the killer of 2003. Wildfires spread around the Mediterranean. Greenland tips into irreversible melt, accelerating sea-level rise and threatening coastal cities. The polar bear and walrus become extinct.
+ 3 °C: Deserts spread across parts of Africa, driving millions of refugees to surrounding countries. A permanent El Niño grips the Pacific, causing weather chaos worldwide. Drought and wild fires rage across the Amazon, destroying swathes of forest, releasing yet more carbon. World food running short. Water shortages threaten parts of India, Pakistan, Australia and Peru.
+4 °C: Tens of millions become refugees as rising waters threaten the Nile Delta and low-lying Bangladesh. The West Antarctic ice sheet collapses, pumping 5 metres of water into global sea levels. Southern Europe becomes like the Sahara, with deserts spreading in Spain and Portugal.
+5 °C: The Earth is hotter than at any time for 55 million years. Desert belts expand across Europe, America and Asia. Some populations try to move towards the poles. Most of the world is uninhabitable.
+6 °C: Huge firestorms sweep the planet as methane hydrate fireballs ignite. Seas release poisonous hydrogen sulphide. Most of life on Earth has been extinguished. Humanity’s survival is in question.
chapter 3
how much carbon can we live with?
Climate change will get worse if we allow greenhouse gas emissions to grow unchecked. So where are the emissions coming from? And how much more can the planet take?
scientific predictions
Models show that if we go on with business as usual and fail to address greenhouse gas emissions we can expect average temperatures across the world to rise dangerously. Precisely how much warmer it will get is the subject of huge investigation but the Intergovernmental Panel on Climate Change (IPCC) gives a range of between 2.4°C and 6.4°C above preindustrial levels by the end of this century. If we don’t take action, scientists believe the most likely point within that range will be a rise of 4°C by the end of this century – that’s enough to produce catastrophic results.
measuring carbon
The proportion of carbon dioxide in the atmosphere is usually expressed as parts per million by volume (ppmv); this tells us the concentration of carbon dioxide in numbers of molecules per million molecules of air.
Emissions can also be measured by: the weight of carbon dioxide (carbon plus two oxygen atoms) – in grammes, kilogrammes and tonnes – over a period of time. High levels of emissions are measured in millions of tonnes of carbon dioxide or by the weight of carbon alone. One tonne of carbon is equal to 3.67 tonnes of carbon dioxide.
Other greenhouse gases are sometimes expressed in million tonnes of the carbon dioxide equivalent (Mt CO2e) – in other words, the amount of carbon dioxide that would have the same effect.
how high are global emissions?
In a little more than a century human activity has added 200 billion tonnes of carbon to the atmosphere. Today we are pumping out just over 7 billion tonnes of carbon a year – that’s twenty times the weight of all the water in Lake Windermere. It’s also equivalent to 26 billion tonnes of carbon dioxide. A further 1.6 billion tonnes of carbon dioxide emissions each year come from changes in the way we use land – mostly by cutting down forests that, when growing, play a vital role in soaking up carbon dioxide.
Scientists agree that we need to stabilise emissions, then reduce them. But at what level?
