The evidence that the earth’s surface is warming rapidly is now exceptionally strong, and beyond doubt.
Evidence for changes in other aspects of the climate system is also strengthening.
The primary cause of the observed warming and associated changes since the mid-20th century — human emissions of greenhouse gases — is also known with a high level of confidence.
Developments in the science of climate change
Risks associated with a changing climate
Implications of the science for emissions reductions
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- The Critical Decade: Climate science, risks and responses, Climate Commission Secretariat, Department of Climate Change and Energy Efficiency, Commonwealth of Australia, June 2011.
The purpose of this update is to review the current scientific knowledge base on climate change, particularly with regard to
- the underpinning it provides for the formulation of policy and
- the information it provides on the risks of a changing climate to Australia.
[It] starts with [the] observations of [how the climate system] is changing [and] the reasons for [those] changes.
It then focuses on the behaviour of the carbon cycle, which is the primary process in the climate system that policy aims to influence.
Finally, the … issue of certainty in climate science is explored …
[Chapter 2 deals with] our scientific understanding of five major aspects of the climate system that are important for risk assessments across many sectors …
- sea-level rise;
- ocean acidification;
- the water cycle;
- extreme events; and
- abrupt, non-linear and irreversible changes in the climate system.
[It] circumvents the complexity and confusion of the targets/timetables/baselines approach [by adopting] a much simpler budget — or aggregate emissions — analysis.
[This approach is based on the total] amount of emissions, in billions of tonnes of CO2 [equivalents], that global society can emit to achieve a particular temperature limit, such as 2°C above the pre-industrial level.