It’s unequivocal: Humans are warming the planet
For the first time, the IPCC [Intergovernmental Panel on Climate Change] states unequivocally — leaving absolutely no room for doubt – humans are responsible for the observed warming of the atmosphere, lands and oceans.
The IPCC finds Earth’s global surface temperature warmed 1.09℃ between 1850-1900 and the last decade. This is 0.29℃ warmer than in the previous IPCC report in 2013.
THE CURRENT STATE OF OUR CLIMATE
- Global surface temperatures are now about 1.1oC higher than in 1850-1900 with human activities explaining the observed warming. Climate change is already affecting people across the world, particularly through worsening weather and climate extremes.
- Extreme heat and heatwaves have become more frequent and intense over both land1, 2 and the oceans3, 4. For Australia, warming over land has exceeded 1.4oC and consequently heat extremes have increased5.
- Globally averaged rainfall has increased since 1950, and the frequency and intensity of heavy rainfall has increased over most land areas where we have good observations6, including Northern Australia7.
- Human-induced climate change has increased droughts in some regions, including southern Australia.
- The risk of extreme events acting simultaneously (compound events, eg. drought and extreme heat, conditions associated with extreme fire weather8) has increased in many regions, including Australia.
- Based on multiple lines of evidence, new science has improved our confidence that equilibrium climate sensitivity is between 2.5oC-4.0oC, with a best estimate of 3oC9, 10.
- The recent speed of global surface temperature increases and sea level rise are unprecedented over many thousands of years. Temperatures in the last decade are now warmer than at any time during the last 100,000 years.
ACTIONS REQUIRED TO ACHIEVE PARIS TARGETS
There is a near-linear relationship between the cumulative emissions of CO2 by humans and global warming. This allows a carbon budget to be defined for a given warming target, with the proviso that this budget depends on assumptions including climate system feedbacks.
- To limit warming to 1.5oC with a high probability (80%), there is about 300 billion tonnes of CO2 left in the global carbon budget. This would be fully spent in 7–8 years at current rates of emissions.
- Limiting warming to 2oC with a high probability (80%), there is about 900 billion tonnes of CO2 left in the global carbon budget (22 years at current rates of emission).
- Large-scale deployment of carbon removal methods, if feasible, could extend these timelines, but have the potential to have wide-ranging effects on water availability and food production and will be partly compensated by changes in natural sinks.
- Low and very low emission pathways that give a good chance of meeting the Paris Agreement temperature targets also assume negative emissions from the middle of this century, with more CO2 being drawn out of the atmosphere than is emitted.
Overall, the AR6 report is an important step in further solidifying our understanding of climate risk. The conclusions of the report echo strongly previous reports that near immediate and very deep cuts to greenhouse gas emissions are now overdue and any further delay commits us to an escalating risk of climate extremes. At a global scale, current commitments to reductions in emissions remain too small, and the reduction in emissions too slow, to avoid in excess of 2oC warming and multiple consequences to the climate of Australia