GLOBAL WARMING phenomenon known as global warming is a global warning sign we need to heed In this book readers will learn about the greenhouse effect and how it is connected to global warming Much like plants in a greenhouse all of us on Earth are encased in an atmosphere that traps heat from the Sun Carbon dioxide water vapor methane and other gases which do the trapping have been responsible for keeping the planet warm enough for life to thrive The issue before us all now though is that these so called green house gases are increasing some believe dramatically and with them their heat trapping properties Such an increase and its impact on global climate are of great concern Why the increase As readers of this book will discover with the onset of the Industrial Revolution some 200 years ago machines began making the products people used to make by hand That development was foll lowed by advances in transportation such as the advent of the steam engine the car and the airplane These machines running on fossil fuels emit exhaust sharply raising the concentrations of atmospheric gases that had prior to 1800 or so been relatively stable for thousands of years Today about 90 per cent of the power used to run machines
INTRODUCTION comes from the burning of fossil fuels To further complicate matters the widespread cutting down of forests means that trees nature's own carbon dioxide eaters CO is used by trees to make their food are being removed from an equation that they might otherwise help to balance Whetheror not global warming is a natural fluctuation or a human caused phenomenon has been debated in the media though sci entists now widely agree that humans are indeed the cause of the past century's steep temperature rise Evidence collected from thermometers for roughly the past 150 years as well as paleoclimatic data taken from glacial ice cores tree rings and other sources show that the surface temperature on Earth is indeed rising Glaciers are melting animal habitats are dwindling and weather events such as hurricanes typhoons and heat waves seem to be on the rise Read on to discover the science behind the debate the effects rising temperatures are having and are pro jected to have and what the world is doing in
CAPHER GLOBAL WARMING EARTH's CHANGING CLIMATE The rise of air temperatures near Earth's surface over the past century is known as global warming Earth has experienced periods of gradual warming and cooling throughout its existence due to natural causes such as volcanic eruptions and variations in the Sun's output However scientists have attributed the current increase in global temperatures to human causes primarily the release of certain gases into the atmosphere as a result of industrial activity These gases collectively termed greenhouse gases absorb and trap heat emitted from Earth's surface through a phe nomenon known as the greenhouse effect In addition to the rise in near surface air temperatures global warming encom passes other climatic changes caused by this warming such as variations in precipi tation patterns winds and ocean currents For this reason the terms global warm ing and climate change are sometimes used interchangeably IO
GLOBAL WARMING EARTH's CHANGING CLIMATE Sun reflected ight atmosphere absorbed and reradiated Earth Some incoming sunlight is reflected by Earth's atmosphere and sur face but most is absorbed by the surface which is warmed Infrared IR radiation is emitted from Earth's surface Some IR radiation escapes to space but some is absorbed by greenhouse gases and rera diated toward Earth where it further warms the surface and lower atmosphere Encyclopaedia Britannica Inc II
