Lectures by ElenaYulaeva - UC SAN DIEGOaerosols.ucsd.edu/EY_01-01_OverviewOfClimateChange.pdf · A planet's climate is determined by its mass, its distance from the sun, its rotation

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.

OBSERVED CLIMATE TRENDS

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.

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

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.

Over the last 100 years, the global sea level has risen by about 10 to

25 cm.

CSIRO Sea Level Rise Curves, 1992-June 2008

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?

The western states have been warming in

recent decades.

Recent trends:

Geographically, here is the pattern of warming.

(Cayan et al., 2001)

Recent trends:

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

Projected impacts of Climate

Change

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.

Temperature change, 2071-2100 minus 1961-1990

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.

Ice draft in the 1990s is more than a meter thinner than

it was 20 to 40 years earlier.

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