Stockholm Seminar8th June 2010KVA

Prof. Johan RockströmStockholm Resilience Centre

Stockholm Environment Institute

Anthropogenic global environmental change – risks and uncertainties

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PNAS Special Feature: Tipping elements in the Earth System, Jan 2010, vol 106 (49)

Tipping elements in the Earth system – PNAS Special Feature released December 2009

IPCC AR4 2007

Global Mean Temperature Trend

TAR 20-70 cm (9-88 cm) ”high uncertainty”AR4 18-59 cm (18-79 cm) ”larger cannot be excluded”

”Our understanding of these processes is limited. As a result, they are not included in current ice sheet models and there is no consensus as to how quickly they could cause sea level to rise. Note that these uncertainties are essentially one sided. That is, they could lead to substantially more rapid rate of sea-level rise but they could not lead to a significantly slower rate.....”Church et al., 2008. Sea-level rise A post IPCC

Thermal ExpansionGreenlandArticAntarctica

SOURCES ESTIMATES SOURCE ASSUMPTIONS

Thermal Expansion

0.4-0.9 in 300 yrs IPCC TAR (2X ppm))

Weakening of thermohaline circulation

Mountain Glaciers 0.4 m (80 % loss) 0.5 m sea level rise held (IPCC TAR)

Greenland 0.9 m – 1.8 m in 300 yrs

IPCC TAR 0.9 m (local warming 5.5 C)

Rapid melting not included in IPCC estimate

Antarctica WAIS 1-2 m (estimate including disintegration)

Stable ice sheet models inadquate

EAIS stable

Total 2.7 – 5.1 m 2300 1-1.7 m/century Now 3 cm/decade for 0.6 C warming. 3 C warming = 1.4 m/century

S. Rahmstorf and C. Jäger, 2007

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Uncertain uncertainty

ref: Baer and Mastrandrea (2006)

3 ºC 6 ºC

IPCC AR4 Scenarios

2 ºC warming corresponds to a barrier of 2.5 Wm-2 of radient energy added by humans.

This corresponds to 441 ppm CO2eq (range ~350-550 ppm)

We have already added 3 Wm-2 of radiant energy. CO2 (1.65 Wm-2) and non-CO2 GHGs (1.35 Wm-2)

(non-CO2 GHGs are methane (CH4); nitrous oxide (N2O); halocarbons (HCs) which include CFCs, HCFCs, and HFCs; and tropospheric ozone (O3).

What does a 2 ºC limit mean?

Why have we only seen ~0.7 ºC warming so far?

~0.5 C stored in oceans (20 %)

~ 1.2 C masked by cooling aerosols (50 %)

possibly combined with

a climate sensitivity at the lower end of the climate science analyses (but, even if climate sensitivity is 50 % lower than the median sensitivity, the added energy corresponds to ~1.2 ºC)

Ramanathan and Xu, 2010. PNAS, 107 (18) : 8055 - 8062

Masking and avenues to fast track mitigation

Climate Change< 350 ppm CO2 < 1W m2

(350 – 500 ppm CO2 ; 1-1.5 W m2)

Ocean acidificationAragonite saturation

ratio > 80 % above pre-industrial levels

(> 80% - > 70 %)

Ozone depletion< 5 % of Pre-Industrial 290 DU

(5 - 10%)

Global Freshwater Use<4000 km3/yr

(4000 – 6000 km3/yr)

Rate of Biodiversity Loss

< 10 E/MSY(< 10 - < 1000 E/MSY)

Biogeochemical loading: Global N & P Cycles Limit industrial

fixation of N2 to 35 Tg N yr-1(25 % of natural fixation)

(25%-35%)P < 10× natural

weathering inflow to Oceans

(10× – 100×)

Atmospheric Aerosol Loading To be determined

Land System Change

≤15 % of land under crops

(15-20%)

Chemical Pollution Plastics, Endocrine Desruptors, Nuclear Waste Emitted globally

To be determined

Planetary Boundaries

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1970 1980 1990 2000 2004

Gt C

/yr

CO2 from fossil fuels and other sourcesCO2 from land use changeCH4 from agriculture, waste and energyN2O from agriculture and othersF gases

Adapted from Canadell et al., 2007

Terrestrial and Marine Carbon

sinks

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Gt

Carb

on

/yr

ocean

land

Fossil CO2

Land CO2

Agric/waste/energy CH4

Agric/others N2O

CFCs/Tropospheric O3

Ocean acidificationChallenge to marine biodiversity and ability of oceans to function as sink of CO2

• Southern Ocean and Arctic ocean projected to become corrosive to aragonite by 2030-2060

Turley et al 2006

From R. Buddemeier, based on Kleypas et al. 1999

Global emission pathways in compliance with a 2 ºC guardrail

(WBGU 2009)