1. Climate science: answers to 5 faq
Antoine bret
Universidad castilla-la mancha
Advanced Seminars

2. Lots of questions ¿How… What is the Scientific Consensus?
can we talk about climate on the long term?
do we know there’s global warming?
do we know it comes from an ↑ of Greenhouse Gases (GHG)?
do we know these GHG come from us burning Fossil Fuels?
What is the Scientific Consensus?

3. CLIMATE WEATHER Climate vs. weather
How can we talk about climate in 50 years if we cannot know whether it will rain within 30 days?
CLIMATE
Will August be hotter than January in Madrid?
Will it rain on July 15th?
WEATHER

4. Climate vs. weather: Madrid 2014
Temperature
Winter
Spring
Summer
Fall

5. Climate vs. weather: MadriD
Climate, in travel guides
CLIMATE
WEATHER

6. summary
“Climate is what you expect, weather is what you get” (Mike Hulme)

7. A warming?
What goes down: Arctic Sea Ice

8. A warming?
What goes down: Antarctic Land Ice

9. A warming?
What goes down: Greenland Land Ice

10. A warming? What goes down: Glaciers (Himalaya, Alaska, Alps…)
World glacier monitoring service – wgms.ch

11. A warming?
What goes down: Glaciers
“Muir” glacier
Alaska

12. A warming?
What goes down: Glaciers
August 1941
August 2004

13. A warming?
What goes up: Oceans heat content

14. A warming?
What goes up: Global temperature
~ +1

15. A warming? What goes up: Global temperature
IPCC, CLIMATE CHANGE 2013, The Physical Science Basis, p. 409

16. A warming?
What goes up: Seal level = ? + ?

17. A warming? Arctic? Antarctic? Greenland? Land glaciers?
What goes up: Seal level = Oceans warming + Ice melting
Arctic?
Antarctic?
Greenland?
Land glaciers?

18. A warming?
Ice
Melting

19. A warming? Arctic? Antarctic? Greenland? Land glaciers?
What goes up: Seal level = Oceans warming + Ice melting
Arctic?
Antarctic?
Greenland?
Land glaciers?

20. A warming?

21. See climate.nasa.gov/vital-signs
A warming?
What goes up:
Oceans heat content
Global temperature
Sea level
What goes down:
Arctic sea ice
Antarctica land ice
Greenland land ice
Glaciers
Much more than
1 evidence
See climate.nasa.gov/vital-signs

22. summary
“Climate is what you expect, weather is what you get” (Mike Hulme)
There is a Global Warming

23. Why? = e (<1) What’s happening? Crash-course of climate science
Greenhouse
effect x
a (albedo)
s*T4
Radiation Cs
Atm
Sol
What goes in
(1-a)*Cs
What goes out
e*s*T4 =
Mean temperature T

24. Why?
What has changed in this equation?
(1-a)Cs = esT4

25. Why?
What has changed in this equation?
(1-a)Cs = esT4 No No

26. (1-a)Cs = esT4 Why? No No Sun? Atmosphere?
What has changed in this equation?
(1-a)Cs = esT4 No No
Sun?
Atmosphere?

27. Not the Sun Why? Could it be the Sun?
There are natural cycles, but > 20,000 years
Shorter cycles? Yes, 11 years
Solar power at the Earth orbit (W/m2)
~ 0.1% → DT ~ 0.1 degree
Not the Sun

28. Why? It has to be the atmosphere Just check
Greenhouse gases (GHG): H2O (T), CO2 , CH4
+ 42% → DT ~ +1 degree

29. GHG do it Why? It has to be the atmosphere Just check
Greenhouse gases (GHG): H2O (T), CO2 , CH4
How do we know this? See slides 42 & 43
GHG do it
National Oceanic and Atmospheric Administration – climate.gov

30. Why? Nothing new under the Sun…
The ground temperature is increased by the interposition of the atmosphere, because the solar heat finds less obstacles to penetrate the air… than to cross it again once converted into dark heat
Joseph Fourier, 1824
Atmosphere
Ground

31. Why? Arrhenius 1896 Recent ↑ CO2: +3º Nothing new under the Sun…
Our descendants [will] live under a warmer sky and in a less harsh environment than we were granted

32. Why?
Nothing new under the Sun…
New Zealand

33. summary
“Climate is what you expect, weather is what you get” (Mike Hulme)
There is a Global Warming
It comes from an increase of GHG in the atmosphere

34. Where are they from? Volcanos? NO, for many reasons
Why now? (nothing since 800,000 years)
CO2 would rise by steps
They emit far less than us – 0.5 Gt vs. 30 Gt/year
They cool the planet (observations)

35. Where are they from? Human activity?
A quick calculation, simple and illuminating…
Observations
Computation from human emissions
Desforestation

36. → Where are they from? Human activity?
A quick calculation, simple and illuminating…
More evidences: O2, 13C, 14C →

37. summary
“Climate is what you expect, weather is what you get” (Mike Hulme)
There is a Global Warming
It comes from an increase of GHG in the atmosphere
They come from FF burning

38. Scientific Consensus Do Experts agree? YES
Expert = Someone who participates in the progress of knowledge
How do you form a consensus? Search for the Sources of the Nile
Here, consensus formed in the 1990’s
Steven Sherwood
Science controversies past and present
Physics Today, October 2011, page 39

39. Scientific Consensus
Do Experts agree? YES
Today
>97%

40. Scientific Consensus December 2015 25,000 participants 23,000 talks
# Talks “Is there a Warming?” 0
# Talks “What is its Origin?” 0
# Talks “How to counter deniers”? A LOT

41. summary
“Climate is what you expect, weather is what you get” (Mike Hulme)
There is a Global Warming
It comes from an increase of GHG in the atmosphere
They come from FF burning
There is Ample Scientific Consensus

42. Co2 in the paSt? Ice cores Claude Lorius Today’s air bubble
Past air bubble

43. Co2 in the past? Tree rings