Global warming: Evidence, risks and mitigation options (or: Why global warming is an energy issue) Filippo Giorgi Abdus Salam ICTP, Trieste

Transcription

1 Global warming: Evidence, risks and mitigation options (or: Why global warming is an energy issue) Filippo Giorgi Abdus Salam ICTP, Trieste

2 Four frequent questions Is global warming happening? (If yes) Is global warming due to human activities? Why should we worry about global warming? Why global warming is an energy problem?

3 Glacial and interglacial periods have happened at regular intervals due to small variations of the Earth s orbit

4 Since the beginning of the industrial era ( Anthropocene ) humans have injected into the atmosphere many types of pollutants

5 The Greenhouse Effect Greenhouse gases (GHG) absorb the infrared radiation emitted by the surface of the Earth and re-emit it in all directions (including downward) thereby warming the atmosphere and oceans The main GHGs are H2O, CO2, O3, CH4, N2O, CFCs In 1896 Arrhenius estimated that doubling of CO2 would lead to a global warming of 5-6 C

6 The beginning of the story: C. Keeling s measurements at Mauna Loa, Hawaii CO2 concentration at Mauna Loa (Hawaii)

7 The greenhouse gas concentration in the atmosphere is sharply increasing The isotopic composition of CO2 and the ratio of oxygen to nitrogen confirm that the increase in CO2 is mostly from fossil fuel burning CO2 CH4 N2O CO2 CH4 N2O

8 Why does the increase in GHG concentrations cause global warming? The importance of feedback processes Direct radiative forcing by the increased GHG amounts (positive) Water vapor feedback mechanism (positive) Ice-albedo feedback mechanism (positive) Carbon feedback mechanism (positive) Cloud feedback mechanism (positive or negative)

9 Question 1: Is global warming happening?

10 vidence 1: The global temperature of the Earth s surface has increased by about 0.9 degrees in the last 100 years

11 Detrending the El Nino signal from the long term trend

12 Geographical distribution of warming

13 Evidence 2: Melting of glaciers and snow Pizzo Bernina, 1978 Pizzo Bernina, 2003 Alps

14 Evidence 3: Melting of the arctic ice September Arctic Ice

15 Evidence 4: Sea level rise Global sea level rise has been about 20 cm since 1880

16 Sea level rise in Trieste (Fabio Raicich, CNR Trieste)

17 Evidence 5: Heat absorption by the oceans

18 Answer to question 1 Global warming is Inequivocal (IPCC 2007/13)

19 Question 2: Is the observed global warming due to increased anthropogenic GHG or to natural factors? (Attribution issue)

20 Human Greenhouse gases Volcanic activity Natural factors factors Atmospheric aerosols The earth s climate can change because of anthropogenic or natural factors Variations of Solar radiatios Land-use change Natural variability (ENSO, NAO)

21 Fingerprinting of the anthropogenic effects other GHGs aerosols volcanic solar natural internal Climate models

22 Many studies have shown that most of the warming since the mid 20 th century is due to the increase in greenhouse gases of anthropogenic origin (>95%, IPCC 2013)

23 Can 20 th century warming be due to natural variability? Marcott et al. Science 2013 The current rate of warming is unprecedented in the Holocene (last 11,500 years)

24 Question 3: Why worry about global warming?

25 Climate models predict a further global warming of up to 4-5 C by 2100 in the most pessimistic scenarios ( business as usual )

26 Sea level rise damages coastal areas Coastal floding salt water intrusion Storm surges Global sea level could rise by up to 1 m by 2100 in the high end scenarios

27 Glacier melting reduces the availability of fresh water Kilimangiaro, 1993 Pizzo Bernina, 1978 Pizzo Bernina, 2003 Kilimangiaro, 2000 Ghiacciaio del Forni

28 The greater energy and water content of a warmer atmosphere leads to the intensification of the hydrologic cycle Increase of precipitation intensity and flood risk It rains less frequently but more intensely Increase of droughts and heat waves

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31 Changes in climate can have a strong spatial variability (A1B scenario, ) Temperature change DJF Precipitation change DJF BOREAL WINTER BOREAL WINTER Temperature change JJA Precipitation change JJA BOREAL SUMMER BOREAL SUMMER

32 Climate change will not be felt equally by all nations Tension and disputes for key resources such as water food and energy might increase. The development of some regions might be put at risk, and could lead to great migrations ( climate refugees )

33 Strong warming beyond the 21 st century could lead to semi-irreversible tipping points. Collapse of the deep ocean circulation Melting of Greenland and West Antarctica Ice (sea level rise of > 12 m) Disappearance of the Amazon forest

34 What can 4-6 degrees of global temperature change do on the long term? Global temperature was 4-6 degree lower than today and global sea level about 125 m lower than today

35 Question 4. Why is global warming an energy problem?

36 The impacts of global warming increase with the amount of greenhouse gases in the atmosphere

37 The key of the debate is how to stabilize the concentrations of greenhouse gases and the associated warming below the danger threshold 2 C (1.5 C?) Manage the unavoidable and avoid the unmanageable

38 Estimating the danger threshold Cost of Mitigation Cost of Impacts Cost Danger Threshold Stabilization temperature

39 Global energy consumption

40 The reduction of greenhouse gas emissions implies a conversion to low carbon intensive energy sources Energy efficiency Reforestation and carbon storage Renewable energies Nuclear?

41 Potential of GHG emission reduction One single solution is not available but different portfolios of policies suitable for each country are needed

42 kwh/person The example of California 14,000 Per Capita Electricity Sales (not including self-generation) (kwh/person) (2006 to 2008 are forecast data) 12,000 10,000 United States 8,000 6,000 California 4,000 2,000 France W. Europe Spain Portugal 0

43 The cost of energy: Energy Returned over Energy Invested (EROI)

44 The costs of stabilization are affordable Source: IPCC TAR Working Group III

45 Final considerations The problem of global warming can be summarized with the sentence Manage the inevitable (adaptation) and avoid the unmanageable (mitigation). Mitigation relies on a shift to less carbon intensive energy sources. This should be seen as an opportunity (green economy) rather than a threat for the sutainable development of societies The problem can be solved (or kept under control) at affordable costs, and despite the uncertainties present in climate change science inaction is not justified

46 THANK YOU

47 Loss of biodiversity Many species have already disappeared because of global warming

48 Expansion of some illnesses Vector borne diseases (Malaria) Heat stress Pollen related diseases (Ashtma)