Lectures by ElenaYulaeva - UC SAN DIEGOaerosols.ucsd.edu/EY_01-01_OverviewOfClimateChange.pdf · A...
Transcript of Lectures by ElenaYulaeva - UC SAN DIEGOaerosols.ucsd.edu/EY_01-01_OverviewOfClimateChange.pdf · A...
Lectures by [email protected];858-534-6278
1. 07-13: Overview of Climate Change
2. 07-15:Climate change modeling (topic for research project)
3. 07-18:Forecasting climate (topic for research project)
4. 07-20: Ocean Mixing
5. 07-22: Types of Climate Change . Roundtable on Global
Warming.
6. 07-27: Global Warming, Adaptation & Ethics (topic for
research)
7. 07-29: Climate Change & Impact on Ecosystems
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
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.
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.
.
Without the Greenhouse Effect the Temp of the Surface ~ -18 °C
Actual Temp ~ +14 °C (i.e. +33 °C difference)
Radiative forcing can be used to estimate a subsequent change in equilibrium surface
temperature (ΔTs) arising from that radiative forcing via the equation:
where λ is the climate sensitivity, ~0.8 K/(W/m2), and ΔF is the radiative forcing.
Radiative forcing =
change in the
balance between
radiation coming
into the atmosphere
and radiation going
out.
2005 radiative forcings as
estimated by the IPCC.
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
CO2 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 1958. Differs from global
CO2 at the surface
Red = monthly mean values
black =same, after correction for the average
seasonal cycle (seven seasonal cycles
running mean)
Atmospheric CO2 has increased from a pre-industrial
concentration of about 280 ppmv to about 367 ppmv in 2000
(ppmv= parts per million by volume).
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.
Total CO2 Emissions, Excluding Land Use Change, 2000
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.
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
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.
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.
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 CO2, 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.
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.
Global composite temp.: +0.31 C above 30-year average for June.
Northern Hemisphere: +0.38 C above 30-year average for June.
Southern Hemisphere: +0.25 C above 30-year average for June.
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.
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.
Mike DettingerUS Geological Survey
Scripps Institution of Oceanography
La Jolla, CA
How are California & Western US
hydrologies already changing?
Stewart et al., 2005
Observed:
Warming
Observed:
Less
snowpack
Observed:
Earlier snowfed
streamflow
Observed: Less
snow/more rain;
changing snow
thresholds
Observed: Earlier
greenup dates; more
tree mortalities
Observed:
Enhanced wildfires
This warming has already driven measurable
hydrologic changes.
--> Less snow/more rain
Knowles et al., J. Clim., 2006
-2 std devs
LESS as snowfall
+1 std dev
MORE as snowfall
Rain vs snow
This warming has extended growing seasons.Recent trends:
Cayan et al., BAMS,2001
--> Earlier blooms & greenup dates
The warming has doubled background tree mortality.Recent trends:
Increasing tree mortality rates
Van Mantgem et al., Science, 2009
Warming/drying has increased forest wildfire risks.Recent trends:
Linked wildfire increases & warming
Westerling et al., Science, 2006
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.
Climate models calculate that the global mean surface temperature
could rise by about 1 to 4.5 centigrade by 2100.
Some reports suggest that increase in climate variability or
extremes has taken place in recent decades.
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.
Bangladesh, one of the world's poorest nations is also the country
most vulnerable to sea-level rise.
The figure shows change in cereals production under
three different GCM equilibrium scenarios (percent
from base estimated in 2060).
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.
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.
CALIFORNIA:
Projections of warming by +2 to +6ºC,
likely more so at higher altitudes
Projections of drier dry zones,
mostly small changes in precip
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?
"The era of procrastination is
coming to a close...we are
entering a period of
consequences."-- Winston
Churchill, on eve of WWII
* Already detected across the
West