Climate change projections
While investigating past trends can be an important way of detecting significant shifts in rainfall and temperature patterns, scientists have realised it may be more important to develop computer models of earth/atmosphere interactions under enhanced greenhouse conditions to provide realistic assessments of future climate conditions under long-term climate change.
Global and regional climate models
Global climate models are simplified mathematical representations of the earth’s climate system. They have progressed from static atmospheric models in the 1970s to complex, integrated and dynamic models that now include feedback on land surface, ocean and sea ice, aerosols, carbon cycle and vegetation.
The models are constantly being improved, giving ever greater confidence in climate change science and projections. Because of increased computing capacity, their resolution is also much higher. They have a three-dimensional grid of points over the globe, extending into the ocean and atmosphere. On global models, these points occur about every 300–500 km, while on regional models they occur every 30–60 km, giving more detailed information.
Models are tested for how well they represent past climates and present climatic conditions, including extreme events, year-to-year variability and observed trends. Only models that can simulate the climate adequately are used to develop projections of future climate.
Projections of Queensland’s future climate
Projections of Queensland’s future climate are supplied by CSIRO through a contract with the Queensland Government. These consultancies began in 1995 and a considerable body of knowledge has been developed since then. The following guide to the current level of confidence in projections of Queensland’s future climate shows that:
- there is greatest confidence in the temperature projections, as temperature relates directly to atmospheric concentrations of greenhouse gases
- there is less confidence in rainfall predictions because rainfall fluctuates over years and decades due to influences such as ENSO, the Madden-Julian Oscillation, and the Inter-decadal Pacific Oscillation.
Level of confidence
Very high
- Higher temperatures and changes in extreme temperatures
- Global sea level rise
- Declining soil moisture
High
- Direction of rainfall change (decreasing)
- Increasing potential evaporation (actual depends on many factors)
- Increasing storm surge heights/risk along the east coast of Queensland
- Increasing tropical cyclone intensity
- Increasing temperatures at the regional scale, including extremes
Medium to high
- Increased risk of bushfire
- Increased incidence of extreme rainfall
Moderate
- The overall amount of rainfall decline and seasonality of that change
- Changes in average stream flow
- Increased drought
Low
- Abrupt changes such as melting of polar ice sheets and changes in global ocean currents.
Temperature projections
According to CSIRO projections, the trend towards higher temperatures will accelerate, with increases in average temperatures of between 0.3°C and 2°C by 2030, and between 0.9°C and 6.4°C by 2070, with inland areas tending to warm more rapidly than coastal areas.
As with global temperature increases, future temperature rises in Queensland, including the number of days above 35°C, can be expected to be in the mid- to upper- end of the ranges projected for 2030, and in the mid-range for 2070, due to continuing strong growth in global emissions.
Rainfall projections
Projections of rainfall are more uncertain than those of temperature, with not all models agreeing on whether it is likely to increase or decrease.
An additional concern is the potential for changes in the frequency of El Niño events as it is well known that these have a major influence on Queensland’s climate. In its Third Assessment Report, the Intergovernmental Panel on Climate Change noted that ‘many climate models suggest a more El Niño-like mean state for the future’. Research in this particular aspect related to El Niño frequency under climate change is particularly vital for Queensland’s future.
Evaporation
Potential evaporation is the amount of water that would evaporate from a wet surface in any given climate. Actual evaporation is the amount that actually evaporates, which is usually less than the potential evaporation. It could be zero if there is no water available to evaporate. Projections indicate that annual potential evaporation will increase by up to 13% by 2030, and up to 40% by 2070 over large areas of the state.
Last updated 14 August 2007.