Question 6:

Will a few degrees warming have a significant impact on our climate?

The world has warmed 0.7°C in the past century. Scientists are confident that the world will get warmer in the 21st century due to further increases in greenhouse gas concentrations, with globally averaged surface temperatures likely to increase by 1.1-6.4 °C from 1990 to 2100. Warming of a few degrees may seem minor compared with day-to-day or seasonal variations in temperature. However, in global climate terms it is much larger than any of the climatic changes experienced during the past 10,000 years.

During the last ice age, which was at its maximum about 70,000 years ago, surface temperatures were on average about 5°C lower than today, and much colder in the polar regions. Sheets of ice covered almost one-third of the world's land. The global warming projected in the 21st century would occur at a time that is already one of the warmest for hundreds of thousands of years, with current levels of carbon dioxide not exceeded for the past 650,000 years, and not likely exceeded during the past 20 million years.

A few degrees of global warming will lead to more heat waves and fewer frosts. In Australia, the projected average warming of 0.4 to 2.0°C by the year 2030 would lead to a 10-50 per cent increase in days over 35°C at many places, and a 10-80 per cent decrease in frosts.

More fires and droughts are expected in some regions of the world and more intense rainfall and resultant flooding in other areas. Australia's alpine regions are expected to have less snow cover. Higher latitudes of the globe would receive more rainfall while middle latitudes, including parts of Australia, would be likely to receive less. Tropical cyclones may become stronger. The Intergovernmental Panel on Climate Change Fourth Assessment Report says that sea level is likely to rise by 18 to 59cm by 2100, but this does not include possible changes in big ice sheets such as Greenland and the Antarctic that could lead to more rapid sea level rise. Low-lying coastal areas and islands will be inundated more often by storm surges.

Simulated snow-cover duration (days) for present, 2020 and 2050

PRESENT	2020 LOW	2020 HIGH


2050 LOW	2050 HIGH	DAYS

A low impact climate change scenario for 2020 leads to a 10% reduction in the area with at least one day of snow cover, while a high impact climate change scenario leads to a 40% reduction in area. By 2050, there may be a 20-85% reduction in area.
Graphic courtesy of CSIRO