Is Our Climate Changing?

Is Our Climate Changing? — page 1 — Chapter 1 What is climate change Spring is coming earlier in some parts of the world the ice sheets are melting temperatures are rising Our planet is getting warmer What does all this mean and does it matter Most scientists believe that human activity is changing the climate on earth and that this change may have serious and even catastrophic effects They believe that we must all think about the way we live to try to halt climate change before the damage becomes irreversible Some other people think either that there is no significant change or that human activity is not the cause It is a complex issue yet it is one that affects all of us and that we can’t afford to ignore Is our climate changing All scientists who study the climate agree that there have been changes in the world’s climate over the last hundred years In some parts of the world people have kept temperature records for several hundred years These records show that on average the temperature rose 1 5 F 0 9 C between 1880 and 2012 This may not sound like much but it is enough to make some very real differences including Melting ice The North and South poles and the areas around them the Arctic and Antarctica have vast ice sheets that stretch for hundreds of miles Yet over the last few years these ice sheets have shrunk as rising temperatures have caused them to melt Glaciers frozen rivers in mountainous areas all over earth are also melting Melting permafrost Permafrost is a layer of permanently frozen ground that is found in very cold regions Such ground may not always be covered with snow or ice but 6 Expert View Scientists believe it is 90 percent certain that humans have affected the climate It is extremely likely that human activities have exerted a substantial net warming influence on climate since 1750 Intergovernmental Panel on Climate Change 2007

Is Our Climate Changing? — page 2 — What is climate change normally it never melts completely because the average temperatures in these regions are so low In recent times permafrost has been melting in some areas for the first time in centuries Earlier seasons The arrival of spring is indicated by natural events such as birds nesting and flowers blooming In many places these events are happening earlier than usual because the temperatures that trigger them occur earlier in the year Moving plants and animals Plants and animals are being found in new areas as the climate changes Some places are becoming too hot too dry or too wet to sustain particular animals or plants Other regions have become warmer offering the ideal climate for new species Water pours from a melting iceberg in Disko Bay Greenland 7

Is Our Climate Changing? — page 3 — Is Our Climate Changing The years 1998 2003 2005 2010 2013 and 2014 were the hottest on record Temperatures have been recorded in Britain since 1659 The year 2014 saw the highest average summer temperatures since global records were kept Why the climate changes Climate scientists believe that the changes we are seeing now are the result of greenhouse gases building up in the atmosphere Greenhouse gases are a group of gases that collect in a layer at the top of the atmosphere and act like an insulating blanket keeping heat close to earth They are called greenhouse gases because they behave like the glass walls and roof of a greenhouse they trap heat to keep earth warm Carbon dioxide methane and water vapor are all examples of greenhouse gases Hotter and hotter The earth is heated by the sun About one-third of the heat energy from the sun is reflected straight back into space by clouds and dust in the atmosphere about one fifth warms up the atmosphere around earth and about half actually reaches the surface of earth Some of the heat energy that reaches earth is reflected back particularly from the polar ice caps and up into the atmosphere again Some of this reflected heat passes back through the atmosphere and into space but some is trapped by clouds and greenhouse gases The layer of greenhouse gases reduces the amount of reflected heat that can pass from the earth to space Instead the heat is reflected back from the blanket of gases to the surface once more warming earth again Escaping heat Trapped heat Heat from the sun Heat reflected from the surface Although some of the heat from the sun is reflected back into space some is trapped by the layer of greenhouse gases and remains to warm the surface of the earth 8

Is Our Climate Changing? — page 4 — What is climate change Too much atmosphere and too little The earth’s atmosphere has supported life for millions of years Near neighbors of earth in the solar system show what it’s like to have too little atmosphere or too thick a layer of greenhouse gases They are not planets on which humans could live Venus is earth’s nearest neighbor in space It has a dense atmosphere that is 94 percent carbon dioxide producing an extreme greenhouse effect This atmosphere traps heat near the planet’s surface producing scalding temperatures of around 867 F 464 C The surface of Venus is extremely hot Heat from the sun is trapped by a thick layer of the greenhouse gas carbon dioxide Expert View Although some politicians and business people say that the existence of climate change is still being debated scientists do not disagree about the reality of climate change Consensus as strong as the one that has developed around this topic climate change is rare in science Donald Kennedy editor in chief Science 2001 9

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