Climate Change 2017 The Nature of the Challenge Will Steffen Emeritus Professor, Australian National University Senior Fellow, Stockholm Resilience Centre
Outline of Talk 1. Basic climate science and impacts 2. Implications for New Zealand 3. Climate change and the Earth System: Nature of the challenge
The climate is warming rapidly Global Average Temperature Anomaly, 1900-2016 NOAA 2017
Enhanced Greenhouse Effect
Climate Change: Worsening Extreme Weather
Decline and Death of Coral Reefs
Increase in coral bleaching events: 1960-2010 Time period Number of bleaching events Pre-1980 12 1980s 236 1990s 1874 2000s 5094 Source: Donner et al. 2017
Implications of Climate Change for New Zealand Photos: Net Zero in New Zealand, Vivid Economics
NZ: Emission Reduction Challenge
Comparison of Paris pledges The Climate Institute 2015
Stabilising the Climate: The Carbon Budget Source: IPCC AR5 2013
The Paris 2 o C Target: Can We Meet It? The total carbon budget from 1870 is about 1,000 Gt C for a 66% probability of meeting the 2 o C target. Cumulative human emissions (fossil fuels, cement, land use) from 1870 through 2016 were about 565 Gt C, leaving 435 Gt C in the budget. Accounting for non-co 2 gases (e.g. CH 4, N 2 O) reduces the C budget by 210 Gt C. The remaining budget is 225 Gt C in total. At current rates 10 Gt C per year at current rates, the budget would last a little more than two decades. Sources; IPCC AR5 WGI SPM; GCP 2016
The Paris 2 o C Target: Can We Meet It? The total carbon budget from 1870 is about 1,000 Gt C for a 66% probability of meeting the 2 o C target. Cumulative human emissions (fossil fuels, cement, land use) from 1870 through 2016 were about 565 Gt C, leaving 435 Gt C in the budget. Accounting for non-co 2 gases (e.g. CH 4, N 2 O) reduces the C budget by 210 Gt C. The remaining budget is 225 Gt C in total. At current rates 10 Gt C per year at current rates, the budget would last a little more than two decades. Sources; IPCC AR5 WGI SPM; GCP 2016
Non-CO 2 Greenhouse Gas Emissions Agriculture is main source of emissions CH 4 : Cattle; rice cultivation N 2 O: Fertiliser use IPCC 2013
Changes in the Global Carbon Cycle Le Quéré et al. 2015
Land v. Fossil Carbon Climate Council 2016
Vulnerability of Land Carbon to Reversal Natural disturbances such as bushfires, insect plagues and droughts can all lead to loss of land carbon. These disturbances are being influence by climate change. Increase in soil respiration as temperature rises Changes in land-clearing policies Climate Council 2016
Australia 2016: Bushfires in Tasmania s World Heritage forests This is bigger than us. This is what climate change looks like, this is what scientists have been telling people, this is system collapse. Professor David Bowman, fire ecologist
Land Carbon: The Bottom Line Effective climate change policy must focus on rapid and deep reductions in fossil fuel emissions. Storing carbon in land is also useful, but it is fundamentally different from, and much less important than, reducing fossil fuel emissions. There should be no offsetting of fossil fuel emissions by increasing land carbon storage. There should be separate reporting of fossil fuel emissions and land carbon uptake and loss. Climate Council 2016
NZ: Follow the Swedish Model? Significant carbon tax: Currently 100 USD per tonne CO 2 emitted; proposal to raise tax to 200 USD per tonne. Promotion of wind and solar (!!!) renewable energy generation. Use of large forestry industry for C-neutral power and heat generation. Bio-aviation fuels (C-neutral) plan for Swedish domestic flights. BI-PARTISAN POLITICAL SUPPORT FOR CLIMATE ACTION
Climate Change in a Broader Context The Earth: Patterns of a Complex System Image: NASA
The Nature of the Challenge: Bottom Line 1. MAGNITUDE 2. URGENCY
The Security Risk: Climate Change as a Threat Multiplier The patterns The of where Syrian and Crisis when we can produce Iraqi food refugees will be massively disrupted in a +2 o C world. Millions of humans will be affected. Weak Starvation, government migration, conflict are the likely outcomes. Worst drought in record history - millions flood into cities IPCC AR5 WG1 Report 2013
The Defence Force View
The atmosphere is warming Global Average Temperature Anomaly, 1900-2016 What does this temperature trend mean from an Earth System science perspective? NOAA 2017
Temperature rise: Beyond the envelope of natural variability! Human influence 2000 years of Holocene variability Summerhayes 2015
Rates of Change Rate of increase in ocean acidification is unparalleled for at least the last 300 million years. Rate of atmospheric CO 2 increase over the past two decades is about 100 times the maximum rate during the last deglaciation. Since 1970 the global average temperature has risen at a rate about 170 times the background rate over the past 7,000 years of the Holocene, and in the opposite direction. De Vos et al. 2014; Wolff 2011; Marcott et al. 2013; NOAA 2016; Canfield et al. 2010
Implications of accelerating climate change IPCC temperature projections IPCC 2013
Global Temperature ( C) Earth System moves to a new state? Severe challenge to contemporary civilisation. Possible collapse? 6 5 4 IPCC Projections 2100 AD 3 Committed 2 1 0 Summerhayes 2015
Implications of the Anthropocene Tipping Point? Transition to a new, much hotter state of the Earth System? Return towards a Holocene-like state?
Tipping Elements in the Earth System 10 years of C storage lost in 2005 and 2010 droughts 50 to 250 Gt C lost by 2100 from thawing permafrost Huber, Lenton, and Schellnhuber, in Richardson et al. 2011
Tipping elements and global average temperature Schellnhuber et al. 2016
Tipping Cascades Steffen et al. 2017
The Earth System Perspective: Irreversibility RCP8.5 (BAU) for 2300 RCP8.5 (BAU) for 2100 Clark et al. 2016
Crunch time: Only 3 years away Source: Figueres et al. 2017
Is a 4 o C world inhabitable? Most of the tropics and subtropics will be too hot for human habitation. Changing temperature & rainfall patterns may make current large agricultural zones unproductive. Sea-level rise of 20-40 m ultimately likely, drowning coastal cities, agricultural areas and infrastructure. Maximum carrying capacity of ~1 billion humans (today s population is 7.4 billion)
The Real Nature of Climate Change? What is the difference between a 2 o C and a 4 o C world? Human Civilisation Prof John Schellnhuber Director, Potsdam Institute for Climate Impact Research (PIK)
The Nature of the Challenge Bottom Line A worst-case scenario could collapse modern civilisation. 1. MAGNITUDE 2. URGENCY We have 3 years left to get our act together. Delay rapidly increases risk of collapse.