to the Australian Academy of Science:
No scientific conclusion can ever be absolutely certain.
However, a balanced assessment of the available evidence and prior
knowledge allows us to attach levels of confidence to the findings
of climate science.
There is a high degree of confidence in the broad conclusions of
climate science. We are very confident of several fundamental
conclusions about climate change: that human activities since the
industrial revolution have sharply increased greenhouse gas
concentrations; that these added gases have a warming effect; and
that the Earth's surface has indeed warmed since the Industrial
Revolution. Therefore, we are very confident that human-induced
global warming is real.
"Climate projections" are model-derived estimates of future
Dynamical climate models and emissions or concentration
scenarios are used to produce climate change projections for the
future. Global Climate Model (GCMs) show Queensland's rainfall and
temperature will change into the future leading to warmer climate
with a higher frequency of extreme weather events.
Global climate models have resolutions of hundreds of
kilometres. However regional and more localised projections often
require more point-specific climate information in order to capture
fine-scale climate variations, particularly in regions with complex
topography, coastal locations. To provide such information,
scientists use the 'downscaling approach' to translate the data
from the global climate models in order to provide more localised
information on future climate change.
The modelling shows that some aspects of climate projections
such as rainfall and regional changes are still quite
Climate change models take into account different scenarios.
These scenarios are based on sets of assumptions about possible
alternative futures. Thousands of scientists and other technical
experts involved with the Intergovernmental Panel on Climate Change
(IPCC) have developed a set of future emission scenarios (Special
Report on Emissions Scenarios (SRES) to assess how changes in
economic growth, human population, social trends and technological
advancements will affect future global emissions with consequent
changes to global temperature (because of the 'enhanced' greenhouse
effect) and sea level rise.
The exact amount of warming that will result from any particular
trajectory for future greenhouse gas emissions cannot be projected
precisely, because it depends on details of processes that
reinforce or dampen disturbances to the climate system. Important
processes involve clouds, aerosols, water vapour, ocean
circulations, ice sheets and sea ice, and natural influences on
greenhouse gas levels in the atmosphere.
Despite the uncertainties, climate modelling has an important
role to play in informing public policy on climate change.
Decisions on when and how to respond to climate change involve many
factors that lie outside the realm of science, including ethical
and economic considerations. An appropriate response will depend on
value judgements and an assessment of the risks of various courses
of action. Just as in any other sphere of human activity, decisions
will need to be made before we have absolute certainty about the
The role of climate science is to inform these decisions by
providing the best possible knowledge of climate outcomes and the
consequences of alternative courses of action.
By 2100, our world will have changed in ways that are difficult
to comprehend. Imagine predicting at the beginning of the 19th
century the changes to population and technology that took place
during the next 100 years.