Climate Change - BASIC CONCEPTS - 1.pptx

Climate Change - BASIC CONCEPTS - 1.pptx

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  Climate Change
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  Course Outline  Introduction definitions and explanations;  Global warming;  Parameters of climate change (past trends and future projections;  Causes of climate change and climate (natural and anthropogenic causes),  climate variability.  Impacts of climate change (risks and vulnerability) –  Physical and economic impacts,  Impacts in the various sectors (past, present and future).  Positive effects of climate change in various natural and socio-economic sectors
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  Introduction  Small fluctuationsin the earth’s climate and temperature are nothing new.  Throughout history our ancestors endured droughts, floods and famine.  The climatic fluctuations they faced were relatively small.  The earth’s climate and temperature have been remarkably constant for millennia, with an average temperature of around 15°C to about 33°C warmer than it would have been without a natural greenhouse effect produced by water vapour in the atmosphere.  This introduction to global climate change explains very briefly what has been happening to the world’s climate and why, and what is projected to happen in the future.    Many changes have been observed in global climate over the past century.  The nature and causes of these changes have been comprehensively chronicled in a variety of recent reports, such as those by the Intergovernmental Panel on Climate Change (IPCC).  Until just over two centuries ago the carbon cycle was in balance. But when we discovered that we could unleash the solar energy stored over millennia as coal, gas and oil in carbon reservoirs and use it to drive machines, the amount and the rate at which carbon entered the atmosphere began to increase.  At this rate many times more fossil carbon will be added to the atmosphere over this century than since the industrial era began. If it continues, the atmosphere will look more and more like it did before life appeared. It threatens nothing less than planetary death.
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  What is Weatherand how is it related to Climate WEATHER  Weather is the state of the atmosphere, describing for example the degree to which it is hot or cold, wet or dry, calm or stormy, clear or cloudy. Weather refers to day-to-day temperature and precipitation activity, whereas climate is the term for the averaging of atmospheric conditions over longer periods of time. There are six main components, or parts, of weather:  1) temperature,  2) atmospheric pressure (pressure exerted by the weight of the atmosphere),  3) wind,  4) humidity (water vapour in the air),  5) precipitation, and  6) clouds. Together, these components describe the weather at any given time. The fact that the earth is spherical contributes to the weather. The sun heats up the atmosphere and the earth, but since the earth is spherically, it hits different parts at different times of the day and the year. It also hits at different angles. Areas around the equator get more direct sunlight and are warmer. Areas around the poles get indirect, or angled, sunlight, so they are colder.
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  Weather Contin’d  Theearth is tilted on its axis, giving us the seasons. The different temperatures across the planet as the seasons change cause the atmosphere to move and churn. The movement is what causes wind, clouds, storms, and precipitation. Precipitation is moisture that falls to the ground from clouds in the form of rain or snow. The cycle of warm and cold air mixing and churning creates the weather cycle across the globe.  Weather is driven by air pressure, temperature and moisture differences between one place and another. On the earth's surface, temperatures usually range ± 40 °C annually. Over thousands of years, changes in earth's orbit can affect the amount and distribution of solar energy received by the earth, thus influencing long-term climate and global climate change.  Surface temperature differences in turn cause pressure differences. Higher altitudes are cooler than lower altitudes, as most atmospheric heating is due to contact with the Earth's surface while radiative losses to space are mostly constant.
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  What is ClimateChange?  The free encyclopedia (Wikipedia) defines climate change as:  “a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years.” Encyclopedia Britannica defines it as:  “a periodic modification of Earth's climate brought about as a result of changes in the atmosphere as well as interactions between the atmosphere and various other geologic, chemical, biological, and geographic factors within the Earth system”.  The United Nations Framework Convention on Climate Change (UNFCCC) defines climate change as: “a change in the state of the climate that can be identified (e.g., by using statistical tests) by changes in the mean and/or the variability of its properties and that persists for an extended period, typically decades or longer”. This is further statement to indicate that climate change may be due to natural internal processes or external forces, or to persistent anthropogenic changes in the composition of the atmosphere or in land use.  “a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is, in addition to natural climate variability, observed over comparable time periods.” The UNFCCC thus makes a distinction between climate change attributable to human activities altering the atmospheric composition and climate variability attributable to natural causes.
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  Weather Cont’d  Onearth, the common weather phenomena include wind, cloud, rain, snow, fog and dust storms. Less common events include natural hazards such as tornadoes, hurricanes, typhoons and ice storms. Almost all familiar weather phenomena occur in the troposphere (the lower part of the atmosphere). Weather does occur in the stratosphere and can affect weather lower down in the troposphere, but the exact mechanisms are poorly understood.  Weather occurs primarily due to air pressure, temperature and moisture differences between one place to another. These differences can occur due to the sun angle at any particular spot, which varies by latitude from the tropics. In other words, the farther from the tropics one lies, the lower the sun angle is, which causes those locations to be cooler due the spread of the sunlight over a greater surface.  The uneven solar heating can also be due to the weather itself in the form of cloudiness and precipitation. Higher altitudes are typically cooler than lower altitudes, which are the result of higher surface temperature and radiational heating. In some situations, the temperature actually increases with height. This phenomenon is known as an inversion and can cause mountain tops to be warmer than the valleys below.
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  Definition of ClimateChange Contin’d  In general terms, climate change refers to significant, long-term changes in the global climate. The global climate is the connected system of the sun, the earth and oceans, wind, rain and snow, forests, deserts and savannahs, and everything people do (see Figure 1). The climate of a place, say Buea, can be described as its rainfall and changing temperatures during the year and for decades. But the global climate is more than the “average” of the climates of specific places.
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  Figure 1: Sketchof the system that contributes to the global climate.
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  Climate  Climate isthe characteristic atmospheric condition (weather) based on temperature and rainfall at a particular place or region over time periods – of seasons, years or decades. Temperature is the main factor responsible for climatic changes and there is evidence that human-induced global warming resulting from burning of fossil fuels is changing the climate.  Climate is influenced by a variety of factors, both human-induced and natural. The increase in the carbon dioxide concentration has been the principal factor causing warming over the past 50 years.  Its concentration has been building up in the Earth’s atmosphere since the beginning of the industrial era in the mid-1700s, primarily due to the burning of fossil fuels (coal, oil, and natural gas) and the clearing of forests.  Human activities have also increased the emissions of other greenhouse gases, such as methane, nitrous oxide, and halocarbons.  It is believed that at current trends there will be an increase of 2˚C by 2050. This could result in:  220 million more people at risk from malaria;  12 million more at risk from hunger as a result of failing crops;  2,240 million more people at risk from water shortages, particularly in developing nations.