Climate Change: The science

1. Climate Change: The science UNDP-GEF CBA Workshop June 30 2009 Michael A. Taylor Climate Studies Group, Mona Department of Physics University of the West Indies, Mona

2. QUIZ #1 Context • Weather, climate, climate variability, climate change – all these terms are sometimes confusing. • A. Yes • B. No • C. Not really, but remind me anyway about them. Why Change? How Change? More Change? We Change?

3. Weather and Climate • Weather • Day to day (short term) changes in meteorological parameters – rainfall, temperatures, pressure, etc. • Often perceived in terms of extreme events: heat waves, downpours, cold spells . • Climate • Commonly defined as the “average weather”. Mean and variability of weather over a periods of time ranging from months to thousand/millions of years. • That concerning the status of the entire Earth system, (atmosphere, land, oceans, snow, ice and living things) which serve as the global background condition for determining weather patterns (IPCC 2007) Context Why Change? How Change? More Change? We Change?

4. Variability and Change Context Regular LongTerm Why Change? Trendy Irregular How Change? More Change? We Change?

5. Variability and Change Context • In any climate timeseries multiple timescales of variation exist. • Climate Variability- Regular, Irregular, Long Term • Timescales that are ‘short term’ – seasonal, annual, interannual (every few years), even decadal. – ENSO, AMO, PDV • Good harbinger for climate change impacts. • Climate Change– Trendy • Distinct changes in measures of climate lasting for a long period of time e.g. major changes in temperature, rainfall, snow, or wind patterns lasting for decades or longer. • Variabilityand Change and WeatherExtremes interrelated. • Will examine climate change. Why Change? How Change? More Change? We Change?

6. QUIZ #2 Context • Possible contributors to Climate Change include: • A. Changes in the earth’s orbit • B. Volcanic eruptions • C. Burning of fossil fuels • D. All of the above Why Change? How Change? More Change? We Change?

7. Climate can change due to... Context Why Change? How Change? More Change? We Change?

8. Greenhouse gases? Context Purpose: Glass house to keep plants warm during winter. Why Change? How Change? • How works? • Sun’s rays hit the glass • Some rays immediately reflected • Some pass through glass and reach plants. Inside gets hot. • Heat cannot escape due to glass. • Glass very important!!! More Change? We Change?

9. Greenhouse gases? Atmosphere around earth is like the glass!!! Context Why Change? • How works? • Solar radiation hits atmosphere • 30% reflected. 70% reaches the earth • Earth warms and gives off heat. • Certain gases in atmosphere prevent most of heat escaping. E.g. CO2, methane, H2O, ozone, nitrous oxide • Called greenhouse gases!!! How Change? More Change? We Change?

10. Greenhouse gases? Context Greenhouse effect is not a bad thing = warm (habitable) earth!! Problem Since the Industrial Revolution humans have added a significant amount of greenhouse gases in the atmosphere by burning fossil fuels, cutting down forests and other activities. Why Change? How Change? More Change? We Change?

11. Greenhouse gases? Context Why Change? How Change? More Change? We Change? CO2 A 36% Increase from pre-industrial times. Almost all of the increase is due to human activities (IPCC, 2007) . CH4 Now 148% above pre-industrial levels. (IPCC, 2007) .

12. Greenhouse gases? Context Radiative Forcing How the energy balance of the earth-atmosphere system is altered by factors that affect climate. Why Change? How Change? More Change? We Change?

13. Greenhouse gases? UNDP_GEF CBA Context Why Change? How Change? IPCC (2007) It is extremely unlikely (<5%) that the global pattern of warming during the past half century can be explained without external forcing, and very unlikely that it is due to known natural external causes alone. More Change? We Change?

14. QUIZ #3 Context • Which of the following changes has been observed in the last century: • A. Warmer temperatures • B. More rain • C. Less rain • D. All of the above • E. None of the above Why Change? How Change? More Change? We Change?

15. Global Warming Context Why Change? How Change? More Change? We Change? Global warming is an average increase in temperatures near the Earth’s surface and in the lowest layer of the atmosphere.

16. Global Warming Context Why Change? How Change? More Change? We Change? IPCC: Global warming is unequivocal! There is a greater than 90 percent chance that most of the warming we have experienced since the 1950s is due to the increase in greenhouse gas emissions from human activities.

17. Temperatures Context • Global mean surface temperatures continue to rise. • Earth is 0.75 degrees warmer than in 1860. • 11 of the last 12 years rank among the 12 warmest years on record since 1850. • 7 of 8 warmest years on record have occurred since 2001. • In last 30 years, the rate of warming across the globe has been approximately 3 x greater than the rate over the last 100 years. Why Change? How Change? More Change? We Change?

18. Temperatures Context Why Change? • The warming trend is seen in both daily maximum (day time) and minimum (night time) temperatures. • Minimum temperatures increasing at a faster rate than maximum temperatures. • Land areas have tended to warm faster than ocean areas. • ‘Winter’ months have warmed faster than summer months. How Change? More Change? We Change?

19. Sea Level Rise Context • Primary factors driving current sea level rise include: • the expansion of ocean water caused by warmer ocean temperatures • melting of mountain glaciers and small ice caps • (to a lesser extent) melting of the Greenland Ice Sheet and the Antarctic Ice Sheet Why Change? How Change? More Change? We Change?

20. Sea Level Rise Context • IPCC (2007) • Most of the Pacific and Atlantic basins are experiencing average to above-average sea level rise. • the rate of observed sea level rise increased from the mid 19th to the mid 20th century. During the 20th century, sea level rose at an average rate of  4.8 to 8.8 inches per century (1.2-2.2 mm/year) • Satellite measurements estimate that sea level has been rising at a rate of 9 to 15 inches per century (2.4-3.8 mm/yr) since 1993. Why Change? How Change? More Change? We Change?

21. Rainfall Context Rainfall patterns changing. • IPCC (2007) • Significant changes in amount, intensity, frequency and type of precipitation. • Trends vary widely by region and over time. • Precipitation strongly modulated by variability e.g. ENSO. • Globally there has been no statistically significant overall trend in precipitation over the past century. Why Change? How Change? More Change? We Change?

22. Rainfall Context Rainfall patterns changing. • IPCC (2007) • Precipitation has generally increased over land north of 30°N from 1900-2005, but has mostly declined over the tropics since the 1970s. • Wetter in eastern North and South America, northern Europe and northern and central Asia, but drier in the Sahel, southern Africa, the Mediterranean and southern Asia. • More precipitation now falls as rain rather than snow in northern regions. Why Change? How Change? More Change? We Change?

23. Rainfall Context Proportion of heavy rainfall is increasing over many land areas • IPCC (2007) • There has been an increase in the number of heavy precipitation events over many areas during the past century, as well as an increase since the 1970s in the prevalence of droughts — especially in the tropics and subtropics. • The long-term record emphasizes that patterns of precipitation vary from year to year, and even prolonged multi-year droughts are usually punctuated by a year of heavy rains; for instance as El Niño influences are felt. Why Change? How Change? More Change? We Change?

24. Extreme Events Context • IPCC (2007) • Since 1950, the number of heat waves has increased and widespread increases have occurred in the numbers of warm nights. • The extent of regions affected by droughts has increased as precipitation over land has marginally decreased . • Generally, numbers of heavy daily precipitation events that lead to flooding have increased, but not everywhere. • In the extratropics, variations in tracks and intensity of storms reflect variations in major features of the atmospheric circulation, such as the North Atlantic Oscillation. Why Change? How Change? More Change? We Change? • Tropical storm and hurricane frequencies vary considerably from year to year, but evidence suggests substantial increases in intensity and duration since the 1970s.

25. Caribbean Example Context Why Change? • Study done at UWI and NCDC • Tmax, Tmin, rainfall station data. 1950-2000 • Looking if climate extremes have changed in Caribbean in recent history. How Change? More Change? We Change? Peterson, T. C., M. A. Taylor, et al., 2002: Recent changes in climate extremes in the Caribbean region, J. Geophys. Res., 107(D21)

26. Caribbean Example Context Why Change? How Change? More Change? We Change? • Frequency of cool days and nights decreasing • Frequency of Hot days and hot nights increasing (nights > days) • Trendlines significant at 1% level • Frequency of cool days and nights decreasing • True for rest of world.

27. QUIZ #4 Context • A climate model is: • A. A tool to help us determine future climates • B. A person hired by IBM to show their product • C. A person hired by Mac to show their product Why Change? How Change? More Change? We Change?

28. Climate Models Context • COMPUTER MODELS • A set of physics based equations to describe processes of atmosphere. • Prescribed boundary and initial conditions. • Start with real time and simulate into future (most times to end of century). • Can produce projections of rainfall, temperature, wind, pressure, cloud cover, humidity and a suite of other variables for a day, month, or a year in the future. Why Change? How Change? More Change? We Change?

29. Climate Models Context • Regional Climate Models (RCMs) • Use outputs from GCM as boundary conditions • Horizontal resolution: 25-50 km • Small islands can be resolved. • General Circulation Models (GCMs) • Horizontal resolution: 250-600 km • 10-20 vertical layers in the atmosphere • As many as 30 ocean layers Why Change? How Change? More Change? We Change?

30. Emission Scenarios Context Why Change? How Change? • To generate projections with the climate models we have to make up stories about how the world will evolve in the future. • SCENARIOS = STORYLINES More Change? We Change?

31. Emission Scenarios Context • Most common: IPCC Special Report of Emissions Scenarios (SRES) • Storylines depend on what population growth, energy use, economic development and technology could look like in the future. • A and B families are created to represent different storylines with similar attributes. • Storylines give us estimate of future greenhouse gas concentrations. Why Change? How Change? More Change? We Change?

32. Emission Scenarios Context • B1 (Low Emissions) • Population peaks mid-century and declines thereafter • Rapid change towards a service and information economy • Introduction of clean and efficient technologies • A2 (High Emissions) • Continuously increasing population • Regionally oriented economic development • Technological change more fragmented Why Change? How Change? More Change? We Change? • A1B (Intermediate Emissions) • Global population peaks in mid-century and declines thereafter • Rapid economic growth • Balance across fossil and non-fossil energy sources None involves the stabilization of concentrations of greenhouse gases!!

33. Projections Context Why Change? How Change? More Change? We Change? Models + Scenarios = Future Climate Projection: A potential future evolution of a quantity or set of quantities. Not the same as a Prediction since projections involve some assumptions about the future –and are therefore open to a great deal of uncertainty.

34. Temperatures Context Why Change? How Change? Emission Scenarios More Change? We Change? Commitment No increase in greenhouse gas concentrations from 2000

35. Temperatures Context Why Change? Near-term warming projections are little affected by different scenario assumptions. By 2030 change lies in narrow range of 0.64°C to 0.69°C. How Change? More Change? We Change? End of century Commitment = 0.6 degrees Best-Worst: 1.5 – 5 degrees

36. Temperatures Context Geographic patterns show greatest temperature increases at high northern latitudes and over land, with less warming over the southern oceans and North Atlantic. Why Change? How Change? More Change? We Change? Global mean surface temperatures End of century (A18 medium emissions scenario)

37. Rainfall Context Regional changes (+/-) of up to 20% in average rainfall Generally, robust large-scale patterns: precipitation generally increases in the tropical precipitation maxima, decreases in the subtropicsand increases at high latitudes as a consequence of a general intensification of the global hydrological cycle. Why Change? How Change? More Change? We Change? But… Model projections for extremes of precipitation show larger ranges in amplitude and geographical locations than for temperature. The response of some major modes of climate variability such as ENSO differs from model to model.

38. Sea Level Rise Context • Sea level will continue to rise in the 21st century because of thermal expansion and loss of land ice. • Sea level rise was not geographically uniform in the past and will not be in the future. Why Change? How Change? More Change? We Change? • Projected warming due to emission of greenhouse gases during the 21st century will continue to contribute to sea level rise for many centuries. • Sea level rise due to thermal expansion and loss of mass from ice sheets would continue for centuries even if radiative forcing were to be stabilised.

39. Extremes • Type, frequency and intensity of extreme events are expected to change as Earth’s climate changes. • Changes could occur even with relatively small mean climate changes. • Changes in some types of extreme events have already been observed . Context Why Change? How Change? More Change? We Change? Other… Heat waves become more frequent and longer lasting in a future warmer climate. Increased summer dryness and winter wetness in most parts of the northern middle and high latitudes Precipitationtends concentrated into more intense events, with longer periods of dryin between . Evidence from modelling studies that future tropical cyclones could become more severe, with greater wind speeds and more intense precipitation.

40. Caribbean Example Context Why Change? How Change? More Change? We Change? End of century temperature change (PRECIS RCM) • Irrespective of scenario Caribbean expected to warm • Warming between 1and 5 degrees. • Warming greater under A2 scenario • Warming consistent with projections for other parts of the globe

41. Caribbean Example Context Why Change? How Change? More Change? We Change? End of century % rainfall change (PRECIS RCM) • For both scenarios Caribbean is in general drier. • Up to 30% drier. • Drying more severe under A2 scenario • Far north Caribbean however could be wetter

42. QUIZ #5 Context • In light of all this, should we be concerned? • A. Yes • B. Absolutely yes • C. Yeah Man! • D. This is a rhetorical question, right? Why Change? How Change? More Change? We Change?

43. Confidence Context In light of everything, should we change how we operate? Perhaps depends on how confident we are about the projected changes. Confidence in the models comes from the following: Model fundamentals are based on established physical laws, such as conservation of mass, energy and momentum, along with a wealth of observations. Models ably simulate important aspects of the current climate. Reasonable skill in representing important features of the general circulation across shorter time scales, and aspects of seasonal and interannual variability. Models ably reproduce features of past climates and climate changes. Over several decades models have consistently provided a robust and unambiguouspicture of significant climate warming in response to increasing greenhouse gases. Why Change? How Change? More Change? We Change?

44. Confidence Context So… Though models still show significant errors (mainly due to important small-scale processes not being represented explicitly in models) there is considerable confidence that they are able to provide credible quantitative estimates of future climate change, particularly at larger scales. Why Change? How Change? More Change? We Change?

45. Impact will be widely Felt... Context Why Change? How Change? More Change? We Change?

46. Caribbean example Context Dengue Why Change? How Change? More Change? We Change?

47. Caribbean example Context Why Change? How Change? More Change? We Change? Hot  Wet  Dengue

48. Caribbean example Context Why Change? How Change? More Change? We Change? Linkage to El NiñoDue to rainfall and temperature changes

49. Caribbean example Context Why Change? Estimated that a future 2 degree rise in temperature will cause an increase in incidence of dengue in the Caribbean region. How Change? More Change? We Change?

50. Summary Context Why the Change? Greenhouse gas forcing has very likely caused most of the observed global warming over the last 50 years. How has the Change been manifested to date? Global mean surface temperatures continue to rise. Eleven of the last 12 years rank among the 12 warmest years on record since 1850. Other changes in precipitation patterns, sea levels and extreme events have also been observed. Will there be More Change in the future? Even if concentrations of radiative forcing agents were to be stabilised, further committed warming and related climate changes would be expected to occur. Why Change? How Change? More Change? We Change?