climate change 2017 the nature of the challenge

Climate Change 2017The Nature of the Challenge

Will SteffenEmeritus 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

NOAA 2017

Global Average Temperature Anomaly, 1900-2016

Enhanced Greenhouse Effect

Climate Change: Worsening Extreme Weather

Decline and Death of Coral Reefs

Increase in coral bleaching events: 1960-2010

Source: Donner et al. 2017

Time period Number of bleaching events

Pre-1980 121980s 2361990s 18742000s 5094

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 2oC Target: Can We Meet It?

The total carbon budget from 1870 is about 1,000 Gt C for a 66%probability of meeting the 2oC target.

Cumulative human emissions (fossil fuels, cement, land use) from 1870 through 2016 were about 565 Gt C, leaving 435 Gt C in thebudget.

Accounting for non-CO2 gases (e.g. CH4, N2O) reduces the C budgetby 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 2oC Target: Can We Meet It?

The total carbon budget from 1870 is about 1,000 Gt C for a 66%probability of meeting the 2oC target.

Cumulative human emissions (fossil fuels, cement, land use) from 1870 through 2016 were about 565 Gt C, leaving 435 Gt C in thebudget.

Accounting for non-CO2 gases (e.g. CH4, N2O) 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-CO2 Greenhouse Gas Emissions

IPCC 2013

Agriculture is main source of emissionsCH4: Cattle; rice cultivationN2O: Fertiliser use

Changes in the Global Carbon Cycle

Le Quéré et al. 2015

Climate Council 2016

Land v. Fossil Carbon

Vulnerability of Land Carbon to Reversal

Climate Council 2016

• Natural disturbances such as bushfires, insect plaguesand droughts can all lead to loss of land carbon. Thesedisturbances are being influence by climate change.

• Increase in soil respiration as temperature rises

• Changes in land-clearing policies

Australia 2016:Bushfires in Tasmania’s World Heritage forests

“This is bigger than us. This is whatclimate change looks like, this is whatscientists 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 rapidand 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 emissionsby increasing land carbon storage. There should beseparate reporting of fossil fuel emissions and landcarbon uptake and loss.

Climate Council 2016

NZ: Follow the Swedish Model?

Significant carbon tax: Currently 100 USD per tonne CO2

emitted; proposal to raise tax to 200 USD per tonne.

Promotion of wind and solar (!!!) renewable energygeneration.

Use of large forestry industry for C-neutral power andheat generation.

Bio-aviation fuels (C-neutral) plan for Swedish domesticflights.

BI-PARTISAN POLITICAL SUPPORT FOR CLIMATE ACTION

Image: NASA

Climate Change in a Broader ContextThe Earth: Patterns of a Complex System

The Nature of the Challenge:Bottom Line

1. MAGNITUDE

2. URGENCY

Climate Change as a Threat Multiplier

IPCC AR5 WG1 Report 2013

The patterns of where and when we canproduce food will be massively disrupted

in a +2oC world. Millions of humans will beaffected. Starvation, migration, conflict are

the likely outcomes.

The Syrian Crisis

• Iraqi refugees

• Weak government

• Worst drought in record history -millions flood into cities

The Security Risk:

The Defence Force View

The atmosphere is warming

NOAA 2017

Global Average Temperature Anomaly, 1900-2016

What does this temperature trendmean from an Earth System

science perspective?

Temperature rise: Beyond the envelope of natural variability!

Summerhayes 2015

Human influence

2000 years of Holocene variability

Rates of Change

Rate of increase in ocean acidification is unparalleled forat least the last 300 million years.

Rate of atmospheric CO2 increase over the past twodecades is about 100 times the maximum rate duringthe last deglaciation.

Since 1970 the global average temperature has risen ata rate about 170 times the background rate over the past 7,000 years of the Holocene, and in the oppositedirection.

De Vos et al. 2014; Wolff 2011; Marcott et al. 2013; NOAA 2016; Canfield et al. 2010

Implications of accelerating climate changeIPCC temperature projections

IPCC 2013

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IPCC Projections2100 AD

Earth System moves to a new state? Severe challenge tocontemporary civilisation. Possible collapse?

Summerhayes 2015

Committed

Return towards aHolocene-like state?

Tipping Point?

Transition to a new, muchhotter state of the

Earth System?

Implications of the Anthropocene

Tipping Elements in the Earth System

Huber, Lenton, and Schellnhuber, in Richardson et al. 2011

10 years of C storage

lost in 2005 and 2010

droughts50 to 250 Gt C lost by 2100

from thawing permafrost

Schellnhuber et al. 2016

Tipping elements and global average temperature

Tipping Cascades

Steffen et al. 2017

The Earth System Perspective:Irreversibility

Clark et al. 2016

RCP8.5 (BAU) for 2100

RCP8.5 (BAU) for 2300

Source: Figueres et al. 2017

Crunch time: Only 3 years away

Is a 4oC world inhabitable?

Most of the tropics and subtropics will be toohot for human habitation.

Changing temperature & rainfall patterns may makecurrent large agricultural zones unproductive.

Sea-level rise of 20-40 m ultimately likely, drowningcoastal 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 2oCand a 4oC world?

“Human Civilisation”

Prof John SchellnhuberDirector, Potsdam Institute for Climate Impact Research (PIK)

The Nature of the ChallengeBottom Line

1. MAGNITUDE

2. URGENCY

A worst-case scenario could collapse modern civilisation.

We have 3 years left to get our act together. Delay rapidly increases

risk of collapse.