Lectures by ElenaYulaeva

Transcription

1 Lectures by ElenaYulaeva : Overview of Climate Change :Climate change modeling (topic for research project) :Forecasting climate (topic for research project) : Ocean Mixing : Types of Climate Change. Roundtable on Global Warming : Global Warming, Adaptation & Ethics (topic for research) : Climate Change & Impact on Ecosystems

2 Overview of Climate Change Introduction to Climate Change Observed Climate Trends a) temperatures (ocean+atm) ;b) precipitation (atm); c) sea level (ocean) Projected impacts of Climate Change (applications) a) general; b) ice; c) forests; d) health; e) agriculture ;f) etc

3 A planet's climate is determined by its mass, its distance from the sun, its rotation period and the composition of its atmosphere. Mars is too small to keep a thick atmosphere. Its atmosphere consists mainly of carbon dioxide, but the atmosphere is very thin. The atmosphere of the Earth is a hundred times thicker.

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5 Over the last 400,000 years the Earth's climate has been unstable, with very significant temperature changes, going from a warm climate to an ice age in as rapidly as a few decades. These rapid changes suggest that climate may be quite sensitive to internal or external climate forcings and feedbacks.

6 . Without the Greenhouse Effect the Temp of the Surface ~ -18 C Actual Temp ~ +14 C (i.e. +33 C difference)

7 Radiative forcing = change in the balance between radiation coming into the atmosphere and radiation going out radiative forcings as estimated by the IPCC. Radiative forcing can be used to estimate a subsequent change in equilibrium surface temperature (ΔT s ) arising from that radiative forcing via the equation: where λ is the climate sensitivity, ~0.8 K/(W/m 2 ), and ΔF is the radiative forcing.

8 Global Warming Potential (100 yrs)= relative measure of how much heat a greenhouse gas traps in the atmosphere. It compares the amount of heat trapped by a certain mass of the gas in question to the amount of heat trapped by a similar mass of carbon dioxide. A GWP is calculated over a specific time interval (20, 100, 500 yrs) 1ppmbv=0.001 gram per liter. In 2010 CO2= 388 ppm; Methane=1870; Nitrous oxide=323

9 Red = monthly mean values black =same, after correction for the average seasonal cycle (seven seasonal cycles running mean) CO 2 concentrations in the atmosphere have been measured at an altitude of about 4,000 meters on the peak of Mauna Loa mountain (3400 m) in Hawaii since Differs from global CO2 at the surface

10 Atmospheric CO 2 has increased from a pre-industrial concentration of about 280 ppmv to about 367 ppmv in 2000 (ppmv= parts per million by volume).

11 Total CO2 Emissions, Excluding Land Use Change, 2000 This map depicts the unequal distribution of industry in the world. The significant part of carbon dioxide emissions (~75%)comes from energy production, industrial processes and transport.

12 Emissions of carbon dioxide due to changes in land use mainly come from the cutting down of forests and instead using the land for agriculture or built-up areas, urbanization, roads etc.

13 Over the last 20 years, industrial development has led to a rapid rise in the volume of emissions from Asia, but on a per capita basis, emissions in this region are still at the bottom of the global scale

14 The global carbon cycle shows the carbon reservoirs in Giga tons of Carbon (GtC)and fluxes in GtC/year. Gigaton= billion/one thousand million tons.

15 The amount of aerosols in the air has direct effect on the amount of solar radiation hitting the Earth's surface. Aerosols may have significant local or regional impact on temperature.

16 These radiative forcings arise from changes in the atmospheric composition, alteration of surface reflectance by land use, and variation in the output of the sun. Except for solar variation, some form of human activity is linked to each. Forcing due to episodic volcanic events, which lead to a negative forcing lasting only for a few years, is not shown. The indirect effect of aerosols shown is their effect on the size and number of cloud droplets. A second indirect effect of aerosols on clouds, namely their effect on cloud lifetime, which would also lead to a negative forcing, is not shown. Effects of aviation on greenhouse gases are included in the individual bars. The vertical line about the rectangular bars indicates a range of estimates, guided by the spread in the published values of the forcings and physical understanding. Some of the radiative forcing agents are well mixed over the globe, such as CO 2, thereby perturbing the global heat balance. Others represent perturbations with stronger regional signatures because of their spatial distribution, such as aerosols. For this and other reasons, a simple sum of the positive and negative bars cannot be expected to yield the net effect on the climate system.

17 OBSERVED CLIMATE TRENDS

18 The mean global surface temperature has increased by about 0.3 to 0.6 C since the late 19th century and by about 0.2 to 0.3 C over the last 40 years.

19 Global composite temp.: C above 30-year average for June. Northern Hemisphere: C above 30-year average for June. Southern Hemisphere: C above 30-year average for June.

20 Land T = 7-th;Ocean=11 th warmest since 1880

21 Precipitation has increased over land at high latitudes of the Northern Hemisphere, especially during the cold season. Decrease in precipitation occurred in steps after the 1960s over the subtropics and the tropics from Africa to Indonesia.

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23 Over the last 100 years, the global sea level has risen by about 10 to 25 cm.

24 CSIRO Sea Level Rise Curves, 1992-June 2008

25 Projections and uncertainties (5 to 95% ranges) of global average sea level rise and its components in 2090 to 2099 (relative to 1980 to 1999) for the six IPCC scenarios.

26 How are California & Western US hydrologies already changing? Mike Dettinger US Geological Survey Scripps Institution of Oceanography La Jolla, CA

27 Recent trends: The western states have been warming in recent decades.

28 Recent trends: Geographically, here is the pattern of warming. (Cayan et al., 2001)

29 Observed: Warming Observed: Less snowpack Observed: Less snow/more rain; changing snow thresholds Observed: Earlier snowfed streamflow Observed: Earlier greenup dates; more tree mortalities Stewart et al., 2005 Observed: Enhanced wildfires

30 This warming has already driven measurable hydrologic changes. --> Less snow/more rain -2 std devs LESS as snowfall +1 std dev MORE as snowfall Knowles et al., J. Clim., 2006 Rain vs snow

31 Recent trends: This warming has extended growing seasons. --> Earlier blooms & greenup dates Cayan et al., BAMS,2001

32 Recent trends: The warming has doubled background tree mortality. Increasing tree mortality rates Van Mantgem et al., Science, 2009

33 Recent trends: Warming/drying has increased forest wildfire risks. Linked wildfire increases & warming Westerling et al., Science, 2006

34 Projected impacts of Climate Change

35 If greenhouse gas concentrations keep rising, climatic changes are likely to result. Those changes will potentially have wide-ranging effects on the environment and socio-economic sectors.

36 Climate models calculate that the global mean surface temperature could rise by about 1 to 4.5 centigrade by 2100.

37 Temperature change, minus

38 Some reports suggest that increase in climate variability or extremes has taken place in recent decades.

39 The figure shows a comparison of current vegetation zones at a hypothetical dry temperate mountain site with simulated vegetation zones under a climate-warming scenario.

40 Ice draft in the 1990s is more than a meter thinner than it was 20 to 40 years earlier.

41 Bangladesh, one of the world's poorest nations is also the country most vulnerable to sea-level rise.

42 The figure shows change in cereals production under three different GCM equilibrium scenarios (percent from base estimated in 2060).

43 A warmer climate increases occasions of vector borne tropical diseases. The figure depicts weeks of potential dengue transmission under current temperature and 2 C and 4 C warming.

44 Plasmodium vivax, with the Anopheles mosquito as a vector, is an organism causing malaria. The main climate factors that have bearing on the malarial transmission potential of the mosquito population are temperature and precipitation.

45 CALIFORNIA: Projections of warming by +2 to +6ºC, likely more so at higher altitudes Projections of drier dry zones, mostly small changes in precip "The era of procrastination is coming to a close...we are entering a period of consequences."-- Winston Churchill, on eve of WWII EXPECT significant changes in more rain-vs-snow storms * smaller snowpack amounts * earlier snowmelt timing * greater flood risk earlier streamflow timing * lower low flows (less) overall streamflow earlier/longer growing seasons * recharge? * Already detected across the West