Climate change is a very complex issue; this page provides general information about the topic and is divided into several sections:
What is the difference between the climate and the weather
Climate is essentially a long term description of weather patterns like rain, wind, temperature, sunshine and so on. This description encompasses not just average quantities of the above, but also their range and variability.
The evidence for climate change
What is the evidence for global climate change
The Intergovernmental Panel on Climate Change (IPCC), formed by the World Meteorological Organisation and the United Nations Environment Programme, has conducted a comprehensive review of the scientific evidence for climate change.
In 2007, a report was produced that contained evidence from all continents and most oceans, and shows that many natural systems are being affected by regional climate changes, particularly temperature increases.
Warming of the climate is unequivocal, as is now evident from observations of:
- increases in global average air and ocean temperatures
- widespread melting of snow and ice
- rising global average sea level
A host of detailed global observations provide evidence for climate changes, such as:
- 1995 to 2006 saw eleven of the twelve warmest years on record (since 1850)
- the Earth's average surface temperature has risen 0.74 degrees Celsius since 1900
- heatwaves and extreme rainfall have become more common in many regions
- the sea level has risen 1.8 mm per year since 1961 and the rate is accelerating
- there have been fewer frosts and the ice sheets of Antarctica and Greenland are shrinking
- the timing of physiological processes in plants and animals is changing throughout the world, and populations are shifting their distributions
What is happening in Australia
The CSIRO and Bureau of Meteorology released the technical report Climate Change in Australia in 2007. This report provides the most up to date assessment of climate change in Australia, and includes information from IPCC reports and other information sources.
There have been a number of changes observed in Australia, including:
- average temperatures in Australia rose 0.9 degrees Celsius from 1910 to 2004
- there have been more heatwaves and fewer frosts
- since 1950, annual rainfall has declined on the eastern seaboard and the south of the continent, but increased in the northwest
- since 1973, droughts have become more intense
- since 1973 extreme rainfall events have increased in the northeast and southwest
The causes of climate change
What is causing the increase in temperatures
The majority of international scientists agree that the increase in global average temperatures we are seeing is very likely due to greenhouse gas emissions from human activities.
What is the Greenhouse Effect
Much of the energy which drives the earth's natural processes comes directly from the sun. Around half of the sun's energy that reaches the earth breaks through the atmosphere, warming the surface of the planet. Some of this solar radiation is reflected back into the atmosphere by the land and oceans.
A portion of this reflected heat passes through the atmosphere, but some of it is trapped by atmospheric greenhouse gases.
Greenhouse gases absorb and emit radiation at specific wavelengths within the spectrum of infrared radiation (heat) emitted by the Earth's surface, the atmosphere and clouds. It is this property that causes the greenhouse effect.
What does this mean for our environment
The greenhouse effect keeps temperatures higher than they otherwise would be, just like a glass greenhouse keeps plants warm.
Source: Causes of Climate Change
How has human activity contributed to the Greenhouse Effect
Since the Industrial Revolution human activity, particularly the burning of fossil fuels (coal, oil and natural gas), agriculture and land clearing, has increased the concentration of greenhouse gases in the atmosphere.
Both past and future anthropogenic carbon dioxide emissions will continue to contribute to warming and sea level rise for more than a millennium, due to the timescales required for removal of this gas from the atmosphere.
In response to these challenges, it will be necessary to firstly, reduce greenhouse gas emissions to slow the rate of climate change, and secondly, to prepare strategies to adapt to inevitable climate change.
Reducing Greenhouse Gas Emissions
There is a strong case for urgent action to reduce emission of greenhouse gases. This action must be global to be effective.
Greenhouse gas emissions are produced by a wide range of sources and can be reduced by either modifying our behaviour or by employing technological solutions.
To make significant cuts in emissions cost effectively we need to:
- use energy more efficiently
- ensure the development and uptake of innovative technology
Adaptation to climate change
Despite efforts to reduce greenhouse gas emissions, some level of climate change is inevitable. Even if all greenhouse gas emissions were stopped tomorrow, the Earth would continue warming for decades to come.
On current global trends, global temperatures could rise 2-3° C within the next 50 years and increase by several degrees more by the end of the century.
These apparently small changes in the climate can have big implications for agriculture, health, water, ecosystems and human settlements.
Adaptation is the only way to cope with impacts that are inevitable in the future.
Adaptation means adjusting policies and operations to help prepare our ecosystems, infrastructure and productive sectors to be able to cope with likely climate change impacts. Adaptation strategies and emission reduction measures are a necessary part of addressing this challenge.
The objectives of adaptation measures are to:
- minimise the risks and economic costs of adverse impacts
- take advantage of potential benefits
Climate change in the North-West of NSW
Projected regional climatic changes by 2050 in the New England and North West Region can be summarised as:
- moderate decrease in winter rainfall
- slight to moderate increase in rainfall in other seasons
- drier conditions, particularly in winter and spring, due to the projected increase in temperature
Hotter Climate
- days are projected to be hotter over all seasons, with the greatest warming in winter and spring of 2 to 3oC
- nights are also projected to be warmer, with the mean minimum temperature projected to increase by 2 to 3oC in the east of the region and slightly less in the west
- there are likely to be fewer frosts
Rainfall
- rainfall is projected to increase in spring, summer and autumn by 5-20% often in intense storm events, but decrease in winter by 5-20% with the greatest decrease in the west of the region
- the consequences of changed catchment runoff for streamflow and consumptive water users will depend on what part of the range of potential change is realised and the influence of water infrastructure
- if the drier end of the range of predictions were realised, towns with smaller water supplies would need to consider that there may be inflow reductions of 10-20% during drier periods
- evaporation
- an increase in evaporation is projected to create drier conditions particularly in winter and spring
- in summer the net water balance is projected to remain similar to current conditions
Bushfire
- the frequency of very high or extreme fire-risk days is predicted to increase across NSW
- higher temperatures, evaporation and high fire-risk days are likely to increase fire frequency and intensity across the region
- the fire season is likely to be extended as a result of warmer temperatures
- biodiversity
- higher temperatures and drier conditions are very likely to have a major impact on biodiversity
- higher altitude forests west of the tablelands such as Mount Kaputar and the Liverpool Ranges are likely to undergo major contractions both eastward and upward in response to higher temperatures
- climate change is likely to place additional pressures on those ecological communities that are already stressed due to fragmentation or loss
- fauna are likely to be affected by habitat loss, long hot spells and reduction in key habitat resources such as hollow bearing trees and nectar
- increased fire frequencies are likely to widespread changes across many ecosystems
Soil
- reduced vegetation cover, caused by poorer growing conditions, is very likely to leave some soils vulnerable to increased erosion
- the risk of erosion is likely to be exacerbated by increased rainfall in summer and autumn, but is likely to be reduced on the plains in spring
- gully erosion on the slopes and plains is likely to increase in summer with increased runoff
- wind erosion is likely to increase in the drier areas and the management of sodic soils is likely to be more difficult on the plains
- vulnerable areas include some surface soils on the plains, and gullies on the slopes and plains
- acidification hazard is likely to be slightly reduced
- salinity hazard is likely to change, but the degree of change will vary with the characteristics of local catchments
Floods
- despite the potential for drier conditions for much of the year due to increased evaporation, flood producing rainfall events are likely to increase in frequency and intensity
- the extent to which these changes lead to increased flood levels depends on the existing catchment conditions such as moisture levels in the soils and the water levels in the major storages at the time of the rainfall event
References
The source of this information is the Causes of Climate Change website. The source of local impacts is the Summary of Climate Change Impacts: New England/North West NSW Region, NSW Climate Change Action Plan, NSW Government 2008.