Climate change science and solutions

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1 Climate change science and solutions Professor David Karoly School of Earth Sciences, University of Melbourne ARC Centre of Excellence for Climate System Science

2 Some views from leaders Barack Obama, 2013: We will respond to the threat of climate change, knowing that the failure to do so would betray our children and future generations. Ban Ki Moon, 2009 Climate change is the greatest threat facing humanity. It threatens to undo 50 years of our development work and it will impact the poor in the greatest sense. Kevin Rudd, 2007: Climate change is the greatest moral, economic and social challenge of our time

3 Global mean temperature to 2012

4 Global ocean heat content change From CSIRO/BoM (2012)

5 Indicators of global warming (from State of the Climate 2009, Bull Am Met Soc, 2010)

6 Trends in Australian climate

7 Greenhouse gas concentrations Concentrations in 2011 CO2 = 390 ppm, CO2-e = 473 ppm From CSIRO/BoM (2012)

8 Causes of From climate change

9 Recent global mean temperature variations from model simulations and observations From

10 Observed and modeled minimum Arctic sea-ice extent in September From

11 Conclusions from the IPCC Fourth Assessment in 2007 It is very likely that hot extremes, heat waves, and heavy precipitation events will continue to become more frequent. Snow cover is projected to contract. Sea ice is projected to shrink in both the Arctic and Antarctic. Storm tracks are projected to move poleward, with changes in wind, precipitation, and temperature patterns. Increasing atmospheric CO 2 concentrations lead to increasing acidification of the ocean. 21st century anthropogenic CO 2 emissions will contribute to warming and sea level rise for more than a millennium, due to the long timescales required for removal of this gas.

12 Projections of sea level rise Past sea level and sea-level projections from 1990 to 2100 based on global mean temperature projections of the IPCC TAR.! From Rahmstorf, Science, 2007 From IPCC AR4

13 Projected climate change hotspots in Australia (from IPCC AR4 WGII, chapt 11)

14 Global CO 2 Emissions from Fossil Fuels

15 Avoiding dangerous climate change Meinshausen et al (2009) Business as usual leads to warming of 5 C or more. Cumulative emissions of 1000 Gt CO 2 in gives 25% chance of more than 2 C warming Target 450 ppm CO 2 -e Already 473 ppm CO 2 -e in 2011 Global reductions of about 80% by 2050

16 Emission reduction paths Emission reductions to achieve cumulative emissions of 750 Gt CO 2 during for different emssion peaking dates From WBGU, 2009

17 Australian emissions and projections From DCCEE Australia s emission projections 2010

18 Steps to avoid the worst case Energy efficiency: use less electricity, petrol and coal, and save money Reduce emissions: rapidly convert to low or zero carbon energy sources: solar, wind, wave, tidal Reduce emissions: stop land clearing, deforestation Increase carbon uptake in soils and native vegetation, with co-benefits for many ecosystems Adapt now to current and future impacts Support change in societal and business attitudes and behaviour

19 The Critical Decade: Key messages (2011) Australian Climate Commission! There is no doubt that the climate is changing. The evidence is overwhelming and clear. We are already seeing the social, economic and environmental impacts of a changing climate. It is beyond reasonable doubt that human activities the burning of fossil fuels and deforestation are triggering the changes we are witnessing in the global climate. This is the critical decade. Decisions we make from now to 2020 will determine the severity of climate change our children and grandchildren experience.

20 From

21 References AAS Science of Climate Change Climate Commission Critical Decade report CSIRO & Bur of Met State of the Climate CSIRO Climate change science & solutions for Aust. (free book) My contact information: Prof David Karoly