CLIMATE CHANGE
It’s a hot topic now but earth has changed before
WEATHER OR CLIMATE?
Weather and climate mean two different things. Weather is the type of conditions in the atmosphere over a short period of time (ie hours, days or weeks) and takes into account temperature, rain, how much sun and wind there is and humidity. Climate looks at the bigger picture and patterns over a longer period. Scientists look at average rainfall, temperature, humidity, sunshine, wind speed and the frequency of weather events such as frost and hail — often over 30-year periods.
CHANGES OVER TIME
Earth has experienced some dramatic climate changes and veered between periods of extreme heat and ice. Scientists believe we have had several ice ages that tend to occur every 100,000 years. About 20,000 years ago our planet experienced its last ice age and, since that peak, the planet has gradually warmed. But around 144 to 65 million years ago, earth was still hotter than today. Scientists have found plant and animal fossils that thrive in warm climates in parts of the world that are now much colder, such as traces of breadfruit trees that grow in tropical climates in Greenland.
WHAT’S HAPPENING TODAY?
Ice caps from the last ice age still survive in Antarctica and Greenland. Scientists say earth is now in an “interglacial” period and while increasing temperatures have melted some ice, in many hundreds of years’ time the ice may return. CSIRO and the Bureau of Meteorology are investigating the future of climate change in Australia and forecast hot days will become hotter and more frequent, sea levels will rise, oceans will become more acidic and snow depths will decline. By 2090, winter rainfall is forecast to drop in eastern Australia and southern and eastern states will be at greater risk of severe fire weather. Since 1910, surface air temperatures across Australia have risen by 0.9C and sea levels have risen by about 20cm since the early 1900s.
CAUSES OF CHANGE
Climate change is due to a number of factors — natural and man-made. Phenomena like El Nino and changes in how much sunlight reaches the world’s surface affect temperatures. The movement of the earth’s tectonic plates also affect climate. Historians say that 200 million-plus years ago, our continents were joined and formed one giant land. When continents separated and moved to new locations this affected the way ocean currents flowed that affected climate. Greenhouse gases, such as carbon dioxide, have also contributed to our planet becoming warmer as these gases trap the sun’s heat and keep it close to Earth. People also contribute to greenhouse gases — by burning fuels for industry that pollute the environment and add to global warming. Carbon dioxide levels have increased by more than 20 per cent since the early 1900s.
IMPACT OF CHANGE
Experts believe we are already seeing the effects of climate change and global warming, such as higher temperatures and more frequent heatwaves that are having an impact on plant and animal life. For example, two-thirds of the Great Barrier Reef has suffered coral bleaching that is affecting marine life. Species across the world may struggle to survive as weather becomes warmer and drier. Global warming increases the risk of bushfire and the destruction of natural habitats, homes and human lives. Food security becomes a concern as extended periods of drought force farmers to find crops that withstand hotter, drier days. Increasing heat poses a health threat too, as warm temperatures encourage the spread of disease. Towns and cities may also suffer as infrastructure comes under pressure with increased use of electricity services.