Human influence on the climate is clear, and greenhouse gas emissions are causing the climate to change rapidly. Continued emissions will lead to further warming and risks to natural and human systems. To limit global warming to 2°C, which can reduce severe impacts, emissions must be substantially reduced through coordinated global action. Delay or failure to reduce emissions significantly will make it much harder to limit warming to 2°C and avoid its worst effects.

1. Thomas Stocker
WGI Co-Chair
University of Bern

2. IPCC 5th Assessment Cycle (2008-2014):
Thanks to
WGI Vice Chair
5 Lead Authors
2 Review Editors
of Morocco

3. Human influence on the
climate system is clear.
Continued GHG emissions will
cause further warming and
amplify existing risks.
Changes in climate have
caused impacts in natural
and human systems.
Multiple pathways exist to likely
limit warming to below 2°C.

4. Warming of the climate system
is unequivocal
IPCC2013,Fig.SPM.1b,IPCC2014,Fig.1.1
Anomaly(°C)relativeto1961-1990

5. Human influence on the climate system is clear,
and recent anthropogenic emissions of
greenhouse gases are the highest in history.
IPCC2014,Fig.SPM.1c,d

6. IPCC2013,Fig.SPM.7,IPCC2014,Fig.SPM.6
Global mean surface temperature change from 1986-2005
Further warming will increase the likelihood of
severe, pervasive and irreversible impacts for
people and ecosystems.

7. IPCC2013,Fig.SPM.8,IPCC2014,Fig.SPM.7
Further warming will increase the likelihood of
severe, pervasive and irreversible impacts for
people and ecosystems.
Change in average surface temperature (1986-2005 to 2081-2100)
RCP8.5

8. Further warming will increase the likelihood of severe,
pervasive and irreversible impacts for people and ecosystems.
IPCC2013,TFE.2,Fig.2
+19 cm
+63 cm

9. Global mean warming
All CO2 emissions since 1750

10. Global mean warming
All CO2 emissions since 1750

11. Warming of 0.8 to 2.5°C
1000 billion tons of carbon
Any climate target implies
a limited carbon budget

12. Budget for the 2°C target: 790 bill t C
CO2 emissions until 2014*: −545 bill t C
CO2 emissions in 2014*: 10.1 bill t C
Remaining emissions: 245 bill t C
*updatedfromIPCC2013,WGISPM
Limiting climate change would require substantial and
sustained reductions in greenhouse gas emissions which,
together with adaptation, can limit climate change risks.

14. 2°C world
IPCC2013,Fig.SPM.8,IPCC2014Fig.SPM.7

15. 4.5°C world2°C world
IPCC2013,Fig.SPM.8,IPCC2014Fig.SPM.7

16. 4.5°C world2°C world
Today we have a choice.