CLIMATE CHANGE WHAT IS CLIMATE CHANGE ? Climate change means any significant change in climate, like temperature or rainfall, over a 30 year period or more. If the climate is changing, then the 30 year average temperature, or rainfall, or number of sunny days, is changing. It’s easy to mix up climate and weather! ! ! Here’s a simple way to think about it: climate is what we expect (e.g. cold winters) and weather is what we get (e.g. rain). Weather is what is happening in the atmosphere at any one time: how warm, windy, sunny or humid it is. Climate is the description of the average weather we might expect at a given time, usually taken for several decades or longer to average out year to year variability. Variability might be due to a particularly hot summer or very cold winter. The world’s climate has been getting warmer since 1900. However, this overall warming has not occurred evenly across the world’s surface and different places, because of their location and geography, are affected in different ways. Does the sun cause climate change? It’s true that changes in solar activity does affect global temperatures. Changes in the energy output of the Sun, and the Earth’s orbit around the Sun, do have an effect on the Earth’s climate. Ice ages have come and gone in regular cycles for nearly three million years. There is strong evidence that these are linked to regular variations in the Earth’s orbit around the Sun, the so-called Milankovitch cycles. These cycles change the amount of the Sun’s energy received by different places on the Earth’s surface. However, over the last 50 years, increased greenhouse gas concentrations have had a much greater effect than changes in the Sun's energy. How has the greenhouse effect changed? Naturally occurring gases in our atmosphere, such as carbon dioxide and methane, provide an insulating effect without which the earth would be a frozen planet. However, levels of greenhouses gases in the atmosphere have increased, preventing more heat escaping to Space and leading to ‘global warming’. Any increases in the levels of greenhouse gases in the atmosphere mean that less heat escapes to Space and global temperatures increase - an effect known as 'global warming'. Over the past 150 years in the industrial era, human activities have increased the emissions of three principal green house gases: carbon dioxide, methane and nitrous oxide. These gases accumulate in the atmosphere, causing concentrations to increase with time. Carbon dioxide (CO₂) has increased from our use of fossil fuels which we burn for use in transpor tation, energy generation, building heating and cooling. Deforestation also releases CO2 and reduces its uptake by plants. Methane (CH₄) has more than doubled as a result of human activities related to agriculture, natural gas distribution and landfills. However, increases in methane concentrations are slowing down because the growth of emissions has decreased over the last two decades. What has caused the rise in temperatures over the past 100 years? In the first half of the 20th century global temperatures have risen because of increases in the levels of greenhouse gases in the atmosphere as well as changes in the amount of energy emitted by the Sun. In the second half of the 20th century warming is mainly due to changing greenhouse gas concentrations. Sulphate particles from industrial emissions reflect solar radiation and therefore act to cool climate. These particles helped mask the warming for a few decades from 1940, but then reductions in these pollutants,as they are the cause of poor air quality, together with ever increasing concentrations of greenhouse gases led to renewed warming from the 1970s. What is the greenhouse effect? It is essential to human life! The natural greenhouse gas effect keeps Earth much warmer than it would otherwise be. Without the greenhouse effect, planet Earth would be too cold to support human life as we know it. The temperature of the Earth is determined by the balance between energy coming in from the Sun in the form of visible radiation (sunlight) and energy constantly being emitted from the surface of the Earth to outer space in the form of invisible infrared radiation (heat). The energy coming in from the Sun can pass through the clear atmosphere pretty much unchanged and therefore heat the surface of the Earth. But the infrared radiation emanating from the surface of the Earth is partly absorbed by some gases in the atmosphere, and some of it is re-emitted downwards. The effect of this is to warm the surface of the Earth and lower part of the atmosphere. This is called the greenhouse effect. The absorbing gases in the atmosphere are primarily water vapour (responsible for about two-thirds of the effect) and carbon dioxide. Methane, nitrous oxide, ozone and several other gases present in the atmosphere in small amounts also contribute to the greenhouse effect. Without the greenhouse effect the Earth would be, on average, about 33°C colder than it presently is. What other things can change the climate? There were three volcanic eruptions big enough to affect the climate in the 20thcentury. There were 3 volcanic eruptions big enough to affect the climate in the 20th century – Agung in Indonesia (1963), El Chichon in Mexico (1982) and Pinatubo in the Philippines (1991). Materials (particles) from violent volcanic eruptions can be projected far above the highest cloud, and into the stratosphere where they can significantly increase how much incoming solar energy is reflected. Major volcanic eruptions can reduce average global surface temperature by about 0.5°C for months or even years. Evidence of climate change CHANGE IN NUMBER OF EXTREME EVENTS. THE CLIMATE CHANGE IN THE RECENT PAST. THE CLIMATE CHANGE IN THE PAST. THE CLIMATE CHANGE IN THE PAST The Earth’s climate has always changed, long before we humans existed! There have been warmer and colder periods. For example, in the last ice age, 20,000 years ago, it was about 9°C colder than it is now. CLIMATE CHANGE IN THE RECENT PAST Current global temperatures are warmer than they have been during at least the past five centuries, probably for more than 1000 years. The 17 warmest years on record have all occurred in the last 20 years. During the 20th century there have been two ‘warming phases’: from the 1910s to the 1940s (0.35°C), and more strongly from the 1970s to the present (0.55°C). Alongside the warming, there has been an almost worldwide reduction in the extent and mass of glaciers in the 20th century. We know that the Greenland Ice Sheet is melting, that the thickness and extent of sea ice in the Arctic have decreased in all seasons and that sea level is rising due to thermal expansion of the oceans and melting of land ice. Instrumental observations over the past 150 years show that air temperatures at the Earth’s surface have risen globall RISING SEA LEVEL Sea levels rose on average by 1.7mm a year during the 20th century. Since 1993 levels have been rising by 3mm a year, according to the IPCC. The average temperature of the oceans is also rising, and has increased by 0.10C over the period 1961-2003. Higher sea levels are partly explained by water expanding as it heats up and partly by melt-water from ice sheets and glaciers finding its way into the oceans. This rise in sea levels has obvious consequences for people living in low-lying coastal regions. RISING SEA LEVEL THREAT TO KIRIBATI MELTING ICE Snow and ice are undergoing a "global-scale decline", according to the IPCC. Overall, the world's glaciers are on the retreat. In the extreme north temperatures are rising faster than the global average, and the area covered by Arctic sea ice has been falling since the 1970s. Antarctica and Greenland contain the two largest ice sheets on the planet. Both are "very likely" to be shrinking, according to the IPCC. But the picture is complex. In Greenland ice is being lost around the coasts, but a little thickening is taking place in central regions. Western Antarctica has seen some significant melting, with effects inlcuding the rapid disintegration of the Larsen-B ice shelf in 2002 A WARMER EARTH Our world is getting warmer. Over the last 100 years the average global surface temperature has risen by about 0.74C. This seemingly small rise has already had a significant effect on our planet. For example, the record books have had to be re-written recently, as 11 of the 12 hottest years recorded so far have all taken place since 1995. It is "very likely" that the rising level of carbon dioxide in the atmosphere is the cause of climate change, according to the Intergovernmental Panel on Climate Change (IPCC). Human activities, such as burning fossil fuels, are the primary source behind this increase. Extreme Events As the Earth’s climate gets warmer, the likelihood of some extreme events such as heat waves increases. Scientists believe, the risk of hotter summer has doubled due to human activities such as fossil-fuel burning. Determining whether a specific, single extreme event is due to a specific cause, such as increasing greenhouse gases, is difficult for two reasons: 1) extreme events are usually caused by a combination of many different factors and 2) a wide range of extreme events is normal even in an un changing climate. The likelihood of some extreme events, such as heat waves, has increased with the changing climate, and the likelihood of others, such as extremely cold nights, has decreased. In some regions there have been increases in droughts and floods. The number of days of very heavy rain have in creased in some places. Tropical storm and hurricane frequencies vary considerably from year to year, but evidence suggests substantial increases in intensity and duration since the 1970s. Facts on climate change and health Over the last 50 years, human activities – particularly the burning of fossil fuels – have released sufficient quantities of carbon dioxide and other greenhouse gases to affect the global climate. The atmospheric concentration of carbon dioxide has increased by more than 30% since pre-industrial times, trapping more heat in the lower atmosphere. The resulting changes in the global climate bring a range of risks to health, from deaths in extreme high temperatures to changing patterns of infectious diseases. From the tropics to the arctic, climate and weather have powerful direct and indirect impacts on human life. Weather extremes – such as heavy rains, floods, and disasters like Hurricane Katrina that devastated New Orleans, USA in August 2005 – endanger health as well as destroy property and livelihoods. Approximately 600 000 deaths occurred worldwide as a result of weather- related natural disasters in the 1990s, some 95% of which took place in developing countries. Intense short-term fluctuations in temperature can also seriously affect health – causing heat stress (hyperthermia) or extreme cold (hypothermia) – and lead to increased death rates from heart and respiratory diseases. Recent studies suggest that the record high temperatures in western Europe in the summer of 2003 were associated with a spike of an estimated 70 000 more deaths than the equivalent periods in previous years. Pollen and other aeroallergen levels are also higher in extreme heat. These can trigger asthma, which affects around 300 million people. Ongoing temperature increases are expected to increase this burden. Rising sea levels – another outcome of global warming – increase the risk of coastal flooding, and could cause population displacement. More than half of the world's population now lives within 60 kilometres of shorelines. Floods can directly cause injury and death, and increase risks of infection from water and vector- borne diseases. Population displacement could increase tensions and potentially the risks of conflict. More variable rainfall patterns are likely to compromise the supply of fresh water. Globally, water scarcity already affects four out of every 10 people. A lack of water and poor water quality can compromise hygiene and health. This increases the risk of diarrhoea, which kills approximately 2.2 million people every year, as well as trachoma (an eye infection that can lead to blindness) and other illnesses. Water scarcity encourages people to transport water long distances and store supplies in their homes. This can increase the risk of household water contamination, causing illnesses. Climatic conditions affect diseases transmitted through water, and via vectors such as mosquitoes. Climate-sensitive diseases are among the largest global killers. Diarrhoea, malaria and protein- energy malnutrition alone caused more than 3 million deaths globally in 2004, with over one third of these deaths occurring in Africa. Malnutrition causes millions of deaths each year, from both a lack of sufficient nutrients to sustain life and a resulting vulnerability to infectious diseases such as malaria, diarrhoea, and respiratory illnesses. Increasing temperatures on the planet and more variable rainfalls are expected to reduce crop yields in many tropical developing regions, where food security is already a problem. Steps to reduce greenhouse gas emissions or lessen the health impacts of climate change could have positive health effects. For example, promoting the safe use of public transportation and active movement - such as biking or walking as alternatives to using private vehicles - could reduce carbon dioxide emissions and improve public health. They can not only cut traffic injuries, but also air pollution and associated respiratory and cardiovascular diseases. Increased levels of physical activity can lower overall mortality rates. Climate change is already beginning to transform life on Earth. Around the globe, seasons are shifting, temperatures are climbing and sea levels are rising. And meanwhile, our planet must still supply us – and all living things – with air, water, food and safe places to live. If we don't act now, climate change will rapidly alter the lands and waters we all depend upon for survival, leaving our children and grandchildren with a very different world. Heat-trapping gases emitted by power plants, automobiles, deforestation and other sources are warming up the planet. Scientists project that if emissions of heat- trapping carbon emissions aren’t reduced, average surface temperatures could increase by 3 to 10 degrees Fahrenheit by the end of the century. The planet’s oceans are also warming, which is causing dangerous consequences such as Stronger Storms and Hurricanes Scientific research indicates that climate change will cause hurricanes and tropical storms to become more intense — lasting longer, unleashing stronger winds, and causing more damage to coastal ecosystems and communities. Scientists point to higher ocean temperatures as the main culprit, since hurricanes and tropical storms get their energy from warm water. As sea surface temperatures rise, developing storms will contain more energy. RISING SEA LEVELS Sea level rise from climate change could displace tens of millions of people. As the Earth heats up, sea levels rise because warmer water takes up more room than colder water, a process known as thermal expansion. Melting glaciers compound the problem by dumping even more fresh water into the oceans. Digitally retouched picture of La Manga del Mar in Murcia to show before (top) and after (below) a rise in sea level. Increased Risk of Drought Higher temperatures increase the amount of moisture that evaporates from land and water, leading to drought in many areas. Lands affected by drought are more vulnerable to flooding once rain falls. As temperatures rise globally, droughts will become more frequent and more severe, with potentially devastating consequences for agriculture, water supply and human health. This phenomenon has already been observed in some parts of Asia and Africa, where droughts have become longer and more intense. Increased Risk of Floods In a warmer future climate, most climate models project decreased summer rainfall and increased winter rainfall in most parts of the northern middle and high latitudes. Along with the risk of summer drought, there is an increased chance of episodes of intense rainfall and flooding. More flooding is also expected in the Asian monsoon region and other tropical areas and in a number of major river basins. Climate change could one-fourth of the Earth's species to be headed for extinction by 2050. Rising temperatures are changing weather and vegetation patterns across the globe, forcing animal species to migrate to new, cooler areas in order to survive. The rapid nature of climate change is likely to exceed the ability of many species to migrate or adjust. Experts predict that one- fourth of Earth’s species will be headed for extinction by 2050 if the warming trend continues at its current rate Heat-Related Illness and Disease Climate change brings health risks to the world's most vulnerable communities. As temperatures rise, so do the risks of heat-related illness and even death for the most vulnerable human populations. In 2003, for example, extreme heat waves caused more than 20,000 deaths in Europe and more than 1,500 deaths in India. Scientists have linked the deadly heat waves to climate change and warn of more to come. In addition to heat-related illness, climate change may increase the spread of infectious diseases, mainly because warmer temperatures allow disease-carrying insects, animals and microbes to survive in areas where they were once thwarted by cold weather. Diseases and pests that were once limited to the tropics — such as mosquitoes that carry malaria — may find hospitable conditions in new areas that were once too cold to support them. The World Health Organization (WHO) estimates that climate change may have caused more than 150,000 deaths in the year 2000 alone, with an increase in deaths likely in the future. Economic Loss and Damage Climate change is already affecting economies around the world. Declining crop yields could put hundreds of thousands of people at risk for starvation. Climate change is affecting businesses and economies at home and around the world. If action is not taken to curb global carbon emissions, climate change could cost between 5 and 20 percent of the annual global gross domestic product, according to a British government report. In comparison, it would take 1 percent of GDP to lessen the most damaging effects of climate change, the report says. These global costs will be felt by local communities and businesses: Globally, more intense hurricanes and downpours could cause billions of dollars in damage to property and infrastructure. Declining crop yields due to prolonged drought and high temperatures, especially in Africa, could put hundreds of thousands of people at risk for starvation. High sea temperatures also threaten the survival of coral reefs, which generate an estimated $375 billion per year in goods and services.
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