Climate emergency and climate extremes: Why every year matters

Presentation by IPCC Working Group I Vice-Chair Sonia Seneviratne for the XIV jornadas de comunicacion y devulgacion de cientificas.

1. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
Climate emergency and climate extremes: Why every
year matters
Prof. Sonia I. Seneviratne
Institute for Atmospheric and Climate Science, ETH Zurich
IPCC AR7 Working Group I Vice-chair; IPCC AR6 Coordinating lead author
COSMO-CAIXA, Campus Gutenberg, Barcelona
September 18, 2024

2. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
“Blue marble”, Apollo 17, 1972

3. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
“Sunset over Earth”, NASA, 11/2009

4. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
One question
Europe,
2022
When do we see that the climate crisis is serious?
Pakistan,
2022
Canada,
2023
Libya,
2023
“Driest summer in 500 years”
Record burnt forest area
61’000 deaths from heat
>1’700 deaths
~$30 billion flood damage and
economic losses
Burnt area: 4x CH
CO
2Emissions: 3x Canada
11’000-20’000 deaths
We are in a climate crisis: And the situation worsens every year…

5. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
Klimakrise: GlobaleErwärmung
(https://climate.copernicus.eu/copernicus
-2023-hottest-year-record)
We are in a climate crisis: And the situation worsens every year…

6. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
Klimakrise: GlobaleErwärmung
(https://climate.copernicus.eu/copernicus-summer-2024-hottest-record-globally-and-Europe)
We are in a climate crisis: And the situation worsens every year…

7. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
Klimakrise: GlobaleErwärmung
(https://www.ipcc.ch/report/ar6/wg1/downloads/outreach/IPCC_AR6_WGI_SummaryForAll_Spanish.pdf)
Why is the global mean temperature on Earth increasing?

8. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
Klimakrise: GlobaleErwärmung
(https://www.ipcc.ch/report/ar6/wg1/resources/summary-for-all/)
Why is the global mean temperature on Earth increasing?

9. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
Human-induced greenhouse effect
Why is the global mean temperature on Earth increasing?
(https://www.br.de/)
(https://www.oce.global/sites/default/files/2024-06/OCE_Summary%201%2C5 °C.pdf)

10. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
(https://www.oce.global/sites/default/files/2024-06/OCE_Summary%201%2C5 °C.pdf)
Human-induced greenhouse effect
Why is the global mean temperature on Earth increasing?
Natural greenhouse effect: +33°C (this is good!)
Human-induced greenhouse effect (2023): additional
1.2°C (this is not good! e.g. fever of 38.2°C for body
temperature of 37°C)
(https://www.br.de/)

11. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
Klimakrise: GlobaleErwärmung
Why is the global mean temperature on Earth increasing?
The main issue is the accumulation of the CO
2greenhouse gas in the atmosphere due
to fossil fuel burning
Once emitted stays
centuries to millenia in
the atmosphere
CO
2
(pictures: Freepik, wikimedia, wikipedia)
(https://gml.noaa.gov/ccgg/trends/mlo.html)

12. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
Klimakrise: GlobaleErwärmung
Why is the global mean temperature on Earth increasing?
May 2024:
New record, >426 ppm
This is a 50% increase
compared to pre-
industrial
concentrations
(280ppm)
(https://gml.noaa.gov/ccgg/trends/mlo.html)

13. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
Greenhouse gas effect due to CO
2concentrations is
already estimated since more than 100 years
(Arrhenius, 1896; based on Fourier, Tyndall)
Svante Arrhenius
(Nobel prize in
Chemistry, 1903)
The greenhouse effect & climate science
Greenhouse effect and climate science

14. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
Greenhouse gas effect due to CO
2concentrations is
already estimated since more than 100 years
(Arrhenius, 1896; based on Fourier, Tyndall)
Svante Arrhenius
(Nobel prize in
Chemistry, 1903)
The greenhouse effect & climate science
Science underlying climate models and attribution of
climate signals to human influence is established
since more than 40 years
Syukoro Manabe & Klaus Hasselmann
(¼ & ¼ of 2021 Physics Nobel prize)
Greenhouse effect and climate science

15. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
www.ipcc.ch
2018
2021 20232019 2019 2022 2022
Intergovernmental Panel on Climate Change (IPCC)

16. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
www.ipcc.ch
Intergovernmental Panel on Climate Change (IPCC)
IPCC 6
th
Assessment Report: The Scientific Basis (WGI)
https://www.ipcc.ch/report/ar6/wg1/
234 lead authors from 65
countries
>14’000 references
>78’000 comments
>2’000 pages
Summary for Policymakers:
~10 pages
(Spanish translation:
https://www.ipcc.ch/report/ar6/wg1/downloads/report/
IPCC_AR6_WG1_SPM_Spanish.pdf)

17. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
www.ipcc.ch
Intergovernmental Panel on Climate Change (IPCC)
IPCC 6
th
Assessment Report:
Assessment on changes in extreme
events
IPCC AR6 WGI, Chapter 11 team:
Sonia I. Seneviratne, Xuebin Zhang
Muhammad Adnan, Wafae Badi, Claudine
Dereczynski, Alejandro Di Luca, Subimal
Ghosh, Iskhaq Iskandar, James Kossin,
Sophie Lewis, Friederike Otto, Izidine
Pinto, Masaki Satoh, Sergio M. Vicente-
Serrano, Michael Wehner, Botao Zhou
https://www.ipcc.ch/report/ar6/wg1/downloads/report/
IPCC_AR6_WGI_Chapter11.pdf

18. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
•We already had 1.1°C of global warming
in 2011-2020 compared to 1850-1900
(current best estimate for 2023: 1.2°C)
•This temperature level is unprecedented
in more than 100’000 years
•The largest part of this warming is
irreversible for several hundreds of
human generations
Observed global warming
(IPCC AR6 WG1, Fig. SPM.1)

19. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
•Best estimate of contribution of human
emissions: All of observed warming
(IPCC AR6 WG1, Fig. SPM.2)
Observed global warming

20. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
IPCC SR15
Sources of CO
2emissions:
•Burning of fossil fuels
•Land use (deforestation)
Atmospheric CO
2concentrations and CO
2emissions
The cause of human-induced global warming is clear
(IPCC AR6 WG1, Chapter 5: Figs. 5.6 and 5.5)
The climate crisis is an
energy crisis

21. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
IPCC SR15
(IPCC AR6 WG1, Fig. SPM.10)
Every additional emissions
of CO
2lead to additional
global warming
Very small remaining CO
2
budget for a stabilisation
at ca. 1.5°C (1.6°C)
Cumulative CO
2emissions vs global warming

22. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
Temperature
extremes
Heavy precipitationFloods Droughts Storms Compound
events
Evidence of observed changes in extremes has strengthened
•Human-induced climate change is already affecting many weather and
climate extremes in every region across the globe
•Some recent hot extreme events would have been extremely unlikely to
occur without human influence on the climate system
Observed changes in extremes
(IPCC AR6 WG1; based on Chapter 11, Seneviratne, Zhang, et al. 2021)

23. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
Climate change is already affecting every
inhabited region across the globe: No region
is spared from changes in climate extremes
jHotHot extremes
Extremerainfall
Drought
The Mediterranean region, including
Spain, is a hotspot of changes in hot
extremes and droughts
Observed changes in extremes

24. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
(IPCC AR6 SYR, Figure SPM.1)
Our possible futures

25. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
•Increase in hot extremes in most inhabited regions
of the world
•Heavier precipitation in several regions
•Increased drying in some regions (including Mediterranean
region)
•Irreversible impacts (increase of sea level rise, extinction
of some animal and plant species, in particular coral reefs)
(IPCC SR15, 2018; IPCC AR6, 2021)
Our possible futures: +1.5ºC vs +2ºC
A limitation of global warming to +1.5ºC compared to +2ºC allows to avoid
substantial additional changes in extremes and impacts

26. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
Projected changes
in extremes are
larger in frequency
and intensity with
every additional
increment of
global warming
(IPCC AR6 WG1, Fig. SPM.6; based on Chapter 11, Seneviratne, Zhang, et al. 2021)
Changes in extremes as function of global warming

27. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
Projected changes
in extremes are
larger in frequency
and intensity with
every additional
increment of
global warming
(IPCC AR6 WG1, Fig. SPM.6; based on Chapter 11, Seneviratne, Zhang, et al. 2021)
Changes in extremes as function of global warming

28. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
Projected changes
in extremes are
larger in frequency
and intensity with
every additional
increment of
global warming
(IPCC AR6 WG1, Fig. SPM.6; based on Chapter 11, Seneviratne, Zhang, et al. 2021)
Changes in extremes as function of global warming

29. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
Projected changes
in extremes are
larger in frequency
and intensity with
every additional
increment of
global warming
(IPCC AR6 WG1, Fig. SPM.6; based on Chapter 11, Seneviratne, Zhang, et al. 2021)
Changes in extremes as function of global warming

30. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
Regions with assessed drying at
2°C of global warming
+CAR
(IPCC AR6 WG1, Fig. SPM.6; based on Chapter 11, Seneviratne, Zhang et al. 2021)
Changes in extremes as function of global warming: Droughts

31. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
Multiple changes in extremes, compound events
•Concurrent heatwaves and droughts & fire weather conditions
•Compound flooding (e.g. in coastal areas)
•Concurrent extremes at multiple locations:More frequent, including
in crop-producing areasat 2°C and above compared to 1.5°C
global warming
(IPCC AR6 WG1; based on
Chapter 11, Seneviratne, Zhang, et
al. 2021)
Changes in extremes as function of global warming

32. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
Changes in multiple extreme events means that we experience
less and less “normal conditions”
Need to consider the risks from a global crisis: Disruptions of supply
chains, global economic impacts, risks of conflicts
(Batibeniz et al. 2023, ESD)
Changes in extremes as function of global warming

33. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
(Biess et al. 2024, ERL)
Concurrent extremes

34. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
(Biess et al. 2024, ERL; see also Vogel et al. 2019, Earth’s Future)
Land area increasingly threatened by climate extremes
Extremes: 95th percentile (1850-1900) or higher
Scenario: SSP5-8.5
Concurrent extremes

35. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
(Biess et al. 2024, ERL)
Concurrent extremes
Breadbasket regions affected by climate extremes

36. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
(Biess et al. 2024, ERL)
Concurrent extremes
Breadbasket regions affected by climate extremes

37. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
(IPCC Land report: https://www.ipcc.ch/srccl; 2019)
High risks for global
food supply instabilities
already above 1.5°C
Food supply instabilities: Risks with increasing global warming

38. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
Risks to coral reefs
2°C
1.5°C
Irreversible impacts to biodiversity associated
with higher global warming:
•coral reefs: losses of 70-90% at 1.5°C, losses
of >99% at 2°C
•tripling of insects and doubling of plants and
vertebrates which lose more than half of their
geographic range at 2°C vs 1.5°C of global
warming
(IPCC SR15, 2018)
0°C
Evidence on risks at 2°C vs 1.5°C: Biodiversity

39. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
Evidence on risks at 2°C vs 1.5°C: Mediterranean ecosystems

40. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
Climate change and health
People are are now dying of human-induced climate change
On average, about 1/3 of all
heat-related mortality can be
attributed to human-induced
climate change (Spain: about
30%)
(Vicedo-Cabrera et al. 2021, Nature Climate Change)

41. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
>230 health journals, including “The
Lancet”, publish a joint call to stop
global warming
“The environmental crisis demands a
similar emergency response. Huge
investment will be needed, beyond what
is being considered or delivered
anywhere in the world. […] Better air
quality alone would realise health
benefits that easily offset the global
costs of emissions reductions”
https://www.thelancet.com/journals/lancet/article/
PIIS0140-6736(21)01915-2/fulltext
Climate change and health

42. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
modified from https://pxhere.com/fr/photo/858113

43. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
It’s time for the
emergency
break

44. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
(IPCC SR15)
Stabilization to ~1.5ºC requires
changes which are unprecedented in
terms of scale:
•Immediate reduction of CO
2
emissions on global scale (until 2030:
~50% of 2010)
•Net-zero CO
2emissions at the latest
in 2040 (66% probability) –2050 (50%
probability)
•“Negative emissions” after reaching
net-zero CO
2: At most 10% of present-
day emissions
Scenarios for global warming stabilization at ~1.5°C

45. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
(IPCC AR6 SYR, Figure SPM.5a)
We are not on track!
Current emissions pathways
”Global GHG emissions are projected to peak between 2020 and at the latest before 2025 in global
modelled pathways that limit warming to 1.5°C (>50%) with no or limited overshoot” (IPCC AR6 WG3)

46. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
A journey of a thousand miles starts with a step
(chinese proverb / Lao Tsu)
https://wallpaperaccess.com/mountain-path

47. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
(IPCC AR6 SYR)
“Zero” is more important than ”net”!!
CO
2emissions, rule of thumb:
•-90% decrease of emissions
•10% remaining emissions
•-10% negative emissions (carbon dioxide
removal: afforestation, technologies)
Getting to “Net-zero” is primarily about
reducing CO
2emissions and the consumption
of fossil fuels
What should we do?: “Net-zero” CO
2

48. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
•No more use of fossil fuels (coal, oil, gas)
•Renewable energy
•Clean electricity
•Electrification of energy use
Solar panels Wind energy Electric mobility Geothermal heating
How to reach net-zero CO
2?
~90% reduction of current
CO
2emissions

49. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
•No more use of fossil fuels (coal, oil, gas)
•Renewable energy
•Clean electricity
•Electrification of energy use
Afforestation Carbon capture and
storage
Synthetic fuels
~90% reduction of current
CO
2emissions
•Carbon dioxide removal (waste combustion,
cement), synthetic fuels (planes)
~10% compensation of CO
2
emissions; very small scale
at present (<<1%)
Several caveats
(timing, scale,
effectiveness,
resilience)
How to reach net-zero CO
2?

50. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
•No more use of fossil fuels (coal, oil, gas)
•Renewable energy
•Clean electricity
•Electrification of energy use
Afforestation Carbon capture and
storage
Synthetic fuels
~90% reduction of current
CO
2emissions
•Carbon dioxide removal (waste combustion,
cement), synthetic fuels (planes)
~10% compensation of CO
2
emissions; very small scale
at present (<<1%)
Several caveats
(timing, scale,
effectiveness,
resilience)
How to reach net-zero CO
2?

51. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
(IPCC AR6 WG3, 2022, Fig. SPM.7)
Some good news…
Many solutions exist and can help us make the first steps to decarbonisation!

52. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
(IPCC AR6 WGIII, 2022; Fig. SPM.3)
Some good news…
Changes are starting to happen

53. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
The challenge at stake
We are moving to a new era in human history
Fossil fuel combustion era
Transition away from/
Phase out of fossil fuels*
*IPCC SR15: chapter 2, pp. 118, 122; IPCC AR6 WGII: chapter 5, p. 829; IPCC AR6 WGIII:
chapter 3, pp. 305, 309, 358; chapter 4, p. 440; chapter 6, pp. 690, 691, 705; chapter 10, p.
1110; chapter 12, p. 1308; chapter 16, p. 1658; chapter 17, p. 1742; Index: p. 1980

54. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
Visions for the future
OR

55. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
Conclusions
•It is worth limiting global warming as close as possible to 1.5°C: This aim is
stated in the 2015 Paris agreement and confirmed in the 2021 Glasgow climate
pact. First essential step: Halve CO
2emissions until 2030!
•Every avoided CO
2emission means less global warming and less changes in
extremes for several human generations!
•The main solutions are: renewable energy (solar, wind) and the electrification
of energy use
•We are not on track, but some recent developments go in the right direction:
Decreased prices and increasing use of renewable energy. We should accelerate
change and progress!
Contact: [email protected]

56. Working Group I –The Physical Science Basis
COSMO-CAIXA, Campus Gutenberg, 18.09.2024 Prof. Sonia Seneviratne, ETH Zurich
(https://www.ipcc.ch/sr15/multimedia/video)