However, almost everywhere the weather and climate will be different from what it used to be. By the end of the 21st century, according to the Intergovernmental Panel on Climate Change, average world temperatures are likely to be between 1. This is much larger than the changes observed over the 20th century, and the rate of warming is unprecedented in at least the last 10, years.
Average rainfall across the globe is likely to increase, particularly during winter in northern mid- to high latitudes. Precipitation events are very likely to be more intense over most areas of the globe, as well as a likely increase in summer risk of drought. Warmer conditions will produce more extremely hot days and fewer cold days. Over most of the continent, annual average temperatures will be 0. By , average temperatures are likely to increase by 1 to 6 degrees Celsius.
The temperature ranges quoted indicate the scientific uncertainty associated with the projections. The warming won't be the same everywhere. There will be slightly less warming in some coastal areas and Tasmania, and slightly more warming in the north-west. South-western Australia can expect decreases in rainfall, as can parts of south-eastern Australia and Queensland.
Wetter conditions are possible in northern and eastern Australia in summer and inland Australia in autumn. When combined with the increase in potential evaporation, the changes in rainfall will lead to drier conditions in Australia.
In areas that experience little change or an increase in average rainfall, more frequent or heavier downpours are likely. Conversely, there will be more dry spells in regions where average rainfall decreases.
Most climate models indicate that in many places global warming is likely to increase the frequency and duration of extreme events such as heavy rains, droughts and floods. It is these events that are so often responsible for devastating droughts in Australia.
By the year , the global average sea level is likely to be between 3 and 17 cm higher than the level. By , sea level is projected to rise by approximately 9 to 88 cm, compared with The rate and magnitude of sea-level change will vary from place to place in response to coastline features, changes in ocean currents, differences in tidal patterns and sea-water density, and vertical movements of the land itself.
In some areas, sea level may actually fall. For much of the planet though, sea levels are expected to continue rising for hundreds of years even if atmospheric temperatures stabilise.
If the Earth's atmosphere warms, the upper layers of the oceans will also warm. Like most substances, water expands when heated. Expansion will raise sea level. Land-based ice in temperate regions such as South America and North America will melt more rapidly. Glaciers may retreat. Melting also contributes to increased sea level. The net effect on sea level rise from ice changes in Greenland and Antarctica is likely to be small.
Overall, Antarctica is not warming significantly. Ice shelves, such as those in the Antarctic Peninsula, float and will not change sea level if they disintegrate or melt. You can check this by adding an ice block to water in a glass. Mark the height of the water on the glass and then see what happens to the height after the ice melts.
Global warming may even lead to increased precipitation over Antarctica, which would lock water away in the ice caps. This may offset some of the sea-level rise caused by thermal expansion of water. Australia is a signatory to and has ratified the United Nations Framework Convention on Climate Change, which is now international law.
The Kyoto Protocol would bind many developed nations to greenhouse gas emission targets. However, the Kyoto Protocol target will not lead to stabilisation of carbon dioxide in the atmosphere. The target represents only the first step towards meeting the objectives of the Framework Convention on Climate Change.
Scientists have been regularly measuring the amount of carbon dioxide in air since the late s. We have been monitoring air in the southern hemisphere since the early s.
The collection, held in stainless steel flasks, dates back to the first samples of pristine "baseline" air collected at the Cape Grim Baseline Air Pollution Station in Tasmania in Snow falling in polar regions such as Antarctic continuously traps tiny pockets of air. More snow lands on top and after a while the enclosed air forms a bubble in the ice. In this way, air is preserved for thousands of years. Ice deep below the surface has older air trapped in it than ice at the surface.
Thanks to polar ice, scientists can analyse air dating back more than , years. The best known impact of these particles, called aerosols, is the white haze of pollution visible over heavily industrialised areas of the northern hemisphere, and to a lesser extent over Melbourne and Sydney on high pollution days. This haze reflects some sunlight back to space, and can have a small, cooling effect on climate. Aerosols can also make clouds brighter and last longer, causing them to be more reflective than normal.
This is also likely to cool the planet in some regions. However, the cooling effect of aerosols is largely restricted to the more polluted regions, whereas greenhouse gases are well mixed throughout the entire atmosphere. Scientists use sophisticated computer models of the world's atmosphere, surface and oceans to examine likely future changes to climate due to global warming.
The models work by mimicking or reproducing the way in which the Earth's climate behaves from day to day, and from season to season. They do this for all parts of the globe: the surface, throughout the atmosphere, and for the depths of the oceans. Climate models are good at simulating the broad features of our present climate. Simulated distribution of surface temperatures, winds and precipitation over the seasons are very similar to what is observed.
This gives us confidence that the models adequately represent the important physical and dynamic processes of climate. By comparing results from the two or more simulations allows scientists to assess likely future climate changes. Scientists also study changes that have happened throughout history on geological timescales when greenhouse gas concentrations were higher than today to learn about what may happen in future. The Division studies changes to greenhouse gas concentrations in the atmosphere as well as determining past changes to the make-up of air from bubbles trapped in ice cores.
We are also using powerful scientific tools to establish where greenhouse gases are coming from and what happens to them once they reach the atmosphere.
Divisional scientists also study the way in which the atmosphere, land surfaces and the oceans interact to determine our climate. The research involves satellite remote sensing and aircraft measurements, theory and numerical models and underpins development of more advanced climate models.
We are examining clouds and cloud processes and the interaction of clouds and radiation. For this activity, we use data from satellite and ground-based remote sensing instruments.
We have developed powerful computer-based global and regional climate models, linking models of the atmosphere, biosphere, oceans and sea-ice. By evaluating and applying the latest scientific findings and model results, we also produce scenarios and assessments of likely climatic changes and their impacts for various regions in Australia and overseas.
Of particular interest are future changes to rainfall, the incidence of droughts and floods, tropical cyclone behaviour, evaporation rates and sea level. Greenhouse: questions and answers The greenhouse effect How does the greenhouse effect work? It absorbs most of the sun's ultraviolet radiation UV-B , limiting the amount of this radiation that reaches the surface of the Earth. Because this radiation causes skin cancer and cataracts, the ozone layer plays an important role in protecting human health.
It also prevents radiation damage to plants, animals, and materials. In the s, scientists noticed that the ozone layer was thinning.
Researchers found evidence that linked the depletion of the ozone layer to the presence of chlorofluorocarbons CFCs and other halogen-source gases in the stratosphere. Ozone-depleting substances ODS are synthetic chemicals, which were used around the world in a wide range of industrial and consumer applications.
The main uses of these substances were in refrigeration and air conditioning equipment and in fire extinguishers. Other important uses included aerosol propellants, solvents and blowing agents for insulation foams. To halt the depletion of the ozone layer, countries around the world agreed to stop using ozone-depleting substances. In , the Vienna Convention and the Montreal Protocol became the first treaties in the history of the United Nations to achieve universal ratification.
Substances covered by the protocol are referred to as 'controlled substances'. The main substances include chlorofluorocarbons CFCs , hydrochlorofluorocarbons HCFCs , halons, carbon tetrachloride, methyl chloroform and methyl bromide. The damage to the ozone layer caused by each of these substances is expressed as their ozone depletion potential ODP. These international agreements helped to greatly reduce the worldwide use of ozone-depleting substances in Europe and around the World Figure 1.
Scientific monitoring shows signs that the ozone layer is starting to recover. Full recovery is not expected to occur before the middle of the 21st century. The reduction in ozone-depleting substances has also had a beneficial side-effect.
Ozone-depleting substances are also very potent greenhouse gases, contributing to the phenomenon as other substances widely known to have a greenhouse effect like carbon dioxide CO 2 , methane CH 4 and nitrous oxide N 2 O. Therefore, by reducing emissions of ozone-depleting substances, the Montreal Protocol has protected both the ozone layer and the climate at the same time.
The magnitude of this benefit is substantial. The reduction in ODS emissions expected as a result of compliance with the Montreal Protocol has been estimated globally at giga-tonnes of CO 2 -equivalent between and Velders et al.
In contrast, the reduction target of greenhouse gas emissions under the Kyoto Protocol assuming full compliance by all developed countries is estimated at giga-tonnes of CO 2 -equivalent on average per year between and , compared to base-year emissions. The phasing out of climate-changing ODS under the Montreal Protocol has therefore avoided greenhouse gas emissions by an amount times larger than the target of the Kyoto Protocol for The reduction of ODS emissions is not a uniformly positive story.
In fact it has indirectly led to new problems. Fluorinated gases F-gases have been introduced as substitutes for ODS in many sectors such as refrigeration and air conditioning applications. These gases do not deplete the ozone layer, but they are greenhouse gases. This means that these new gases also contribute to climate change. And to make matters worse, these F-gases often have a far larger impact on the climate than 'traditional' greenhouse gases such as carbon dioxide CO 2.
For example, some F-gases have a greenhouse effect that is up to 23 times more powerful than the same amount of carbon dioxide. Fortunately, the emissions of F-gases are far smaller than those of CO 2 , but the use of F-gases and their presence in the atmosphere have increased since the s. As a result, the significant contribution of the Montreal Protocol to fighting climate change is in danger of being wiped out by the growing importance of F-gas emissions.
There are two approaches to reducing F-gas emissions. The first approach is to avoid the use of F-gases completely by using gases or technologies that are less damaging to the climate.
The second approach is to reduce the use of F-gases in products and equipment. The EU first set out specific policies to reduce F-gas emissions in with the so-called F-gas Regulation , and with a directive limiting F-gases used in air conditioners in cars, the so-called MAC Directive. Accessed: September 14, Baldwin, M. How will the stratosphere affect climate change? Science, , Intergovernmental Panel on Climate Change, Summary for Policymakers. Qin, M. Manning, Z.
Chen, M. Marquis, K.
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