Transcript how does co2 affect climate? - Evans Laboratory: Environmental

GLOBAL CHANGE BIOLOGY
BIOL 3999: Issues in Biological Science
Dr. Tyler Evans
Email: [email protected]
Phone: 510-885-3475
Office Hours: M,W 10:30-12:00 or by appointment
Website: http://evanslabcsueb.weebly.com/
PREVIOUS LECTURE
• How human systems influence Earth systems
EARTH SYSTEMS
• ecosystems
• climate
• geochemical
cycles
HUMAN SYSTEMS
Global
Change
Biology
• socio-economic
development
• production and
consumption
• resource use
HOW ARE HUMANS INFLUENCING
EARTH SYSTEMS?
ALTERING CLIMATE
CLIMATE: refers to the behavior of the atmosphere over a longer period
of time, and usually for a large area.
WEATHER: refers to the conditions of the atmosphere over a short
period of time, such as hours or days, and typically for a local area
HOW IS CLIMATE ALTERED?
The power of a process to alter the climate is estimated by its RADIATIVE
FORCING, the change in the Earth's energy balance due to that process.
RADIATIVE FORCES may be:
POSITIVE
e.g. increases in solar output
NEGATIVE
e.g. volcanic eruptions
Balance between positive and negative radiative forcing determines climate
RADIATIVE FORCING CAN BE CAUSED BY
HUMAN ACTIVITIES
• carbon dioxide emitted from the burning of fossil fuel is presently
the largest single climate forcing agent, accounting for more than
half of the total positive forcing since 1750.
• Carbon dioxide is naturally present in the atmosphere as part of the Earth's
carbon cycle (the natural circulation of carbon among the atmosphere,
oceans, soil, plants, and animals).
• Prior to the industrial revolution, the carbon cycle was approximately in
balance.
SINKS (removes CO2)
• photosynthesis
• oceans
CO2
SOURCES (add CO2)
• respiration
CO2
• Since that time humans have become a source of CO2 by releasing the carbon
stored in fossil fuels
• Currently, inputs of CO2 outpace the ability of the carbon cycle to remove it
from the atmosphere
SINKS (removes CO2)
• photosynthesis
• oceans
CO2
SOURCES (add CO2)
• respiration
• fossil fuels
CO2
A USEFUL ANALOGY
CO2 IS ACCUMULATING IN THE ATMOSPHERE
393 ppm
in 2013
315 ppm in 1958
CO2 IS ACCUMULATING IN THE ATMOSPHERE
KEELING CURVE
•
•
•
•
named fore Charles David Keeling who collected data
based on atmospheric data collected at Mauna Loa, HI
record starts in 1958 and still continues today
longest continuous record of atmospheric CO2
SEASONALITY IN KEELING CURVE
• reflects seasonal differences in photosynthesis (SINK)
• deciduous plants shed leaves in winter and respiration outpaces photosynthesis
• in summer, photosynthesis outpaces respiration
DOESN’T FULLY EXPLAIN SEASONALITY
• when it is winter in Northern hemisphere (i.e. respiration), it is summer in Southern
Hemisphere (i.e. photosynthesis).
• so shouldn’t these differences cancel each other out?
equator
•
•
•
•
major difference in percent land cover between Northern and Southern hemispheres
most land in Southern hemisphere is in tropics where very little seasonal variation
this difference is greatest at temperate latitudes, where deciduous forests dominate
photosynthesis in the Northern hemisphere growing season is greater than the amount
of CO2 respired during winter in the southern hemisphere
HOW DOES CO2 AFFECT CLIMATE?
CO2 is a GREENHOUSE GAS and contributes to the GREENHOUSE EFFECT
• the Sun emits energy that travels to Earth. Because the Sun is very hot, the energy
is emitted in high-energy, short wavelengths that penetrate the Earth's
atmosphere.
HOW DOES CO2 AFFECT CLIMATE?
CO2 is a GREENHOUSE GAS and contributes to the GREENHOUSE EFFECT
• about 30% of the Sun's energy is reflected directly back into space by the
atmosphere, clouds, and surface of the Earth. The rest of the Sun's energy is
absorbed into the Earth's system.
HOW DOES CO2 AFFECT CLIMATE?
CO2 is a GREENHOUSE GAS and contributes to the GREENHOUSE EFFECT
• Because the Earth is cooler than the Sun, the energy is emitted in the form of
infrared radiation, at wavelengths longer than the incoming solar energy.
HOW DOES CO2 AFFECT CLIMATE?
CO2 is a GREENHOUSE GAS and contributes to the GREENHOUSE EFFECT
• greenhouse gases in the atmosphere absorb much of the long-wave energy emitted
from the Earth's surface, preventing it from immediately escaping from the Earth's
system. The greenhouse gases then re-emit this energy, warming the Earth's surface
and atmosphere.
HOW DOES CO2 AFFECT CLIMATE?
CO2 is a GREENHOUSE GAS and contributes to the GREENHOUSE EFFECT
• the increase in the concentration of CO2 has amplified the natural greenhouse effect
by trapping more of the energy emitted by the Earth. This change causes Earth's
surface temperature to increase among other changes.
• greenhouse gases have a POSITIVE RADIATIVE FORCE because they absorb energy
radiating from Earth’s surface, rather than allowing it to be directly transmitted into
space.
CO2 IS NOT THE ONLY GREENHOUSE GAS
THAT AFFECTS CLIMATE
• several other greenhouse gases produced by human activities:
METHANE (CH4)
a colorless, odorless non-toxic gas consisting of
molecules made up of four hydrogen atoms and one
carbon atom.
NITROUS OXIDE(N2O)
is a colorless, non-flammable gas with a sweetish
odor, made up of two nitrogen atoms and one
oxygen atom
SULFUR HEXAFLUORIDE (SF6)
Human made gas containing one sulfur atom and six
fluoride atoms
• human sources of greenhouse gases far exceed natural sources
METHANE
• methane (CH4) is the second most prevalent greenhouse gas emitted in the United
States from human activities.
• methane is emitted by natural sources such as wetlands, however over 60% of total
CH4 emissions come from human activities.
INDUSTRY
• primary source of
methane is
natural gas
AGRICULTURE
LANDFILLS
• enteric
fermentation
• bi-product of
decaying organic
matter
NITROUS OXIDE
• is a colorless, non-flammable gas with a sweetish odor
• nitrous oxide is naturally produced in the oceans and in rainforests
• globally, about 40% of total N2O emissions come from human activities:
FERTILIZER
NITRIC ACID
improve plant
production
also used in fertilizers
CARS
formed in catalytic
converters
BURNING ORGANIC MATTER
NYLON
Component
of nylon
SULFUR HEXAFLUORIDE
• fluorinated gases have no natural sources and only come from human-related
activities
ALUMINIUM
SEMICONDUCTORS
• these compounds were produced as an alternative to chlorofluorocarbons (CFCs),
which were responsible for depleting the ozone layer
• ironically, these compounds are potent greenhouse gases with long atmospheric
lifetimes
GREENHOUSE GASES THROUGH TIME
CARBON DIOXIDE
GREENHOUSE GASES THROUGH TIME
METHANE
GREENHOUSE GASES THROUGH TIME
NITROUS OXIDE
GREENHOUSE GASES THROUGH TIME
SULFUR HEXAFLUORIDE AND RELATED COMPUNDS
NOT ALL GREENHOUSE GASES ARE CREATED EQUAL…
ATMOPSHERIC CONCENTRATIONS OF ALL THESE
GREENHOUSE GASES ARE INCREASING
2008
economic
crisis
2008 Global CO2 Emissions
• from fossil fuel combustion and some industrial processes (million metric tons of CO2)
• half of emissions
are coming from
two countries
• not corrected for
population (i.e. per
capita)
WILL THE TREND OF INCREASING GREEENHOUSE GASES
CONTINUE?
FUTURE GREENHOUSE GAS EMISSION SCENARIOS
Predictions focus on carbon dioxide:
• other greenhouse gases track the pattern of CO2
• CO2 is by far the largest source of greenhouse gases
A CO2 PROBLEM
U.S.A (84%)
WORLD (77%)
FUTURE CO2 EMISSIONS SCENARIOS
• goal of developing future emission scenarios is not to predict the future
• understand what futures are possible and where major points of uncertainty lie
• inform how present-day decisions will influence a range of possible futures
FUTURE CLIMATE MODELS
• to develop future emission scenarios and how this will impact climate scientists use
MODELS: a mathematical representation of the interactions between human activities
and key components of the Earth systems.
• to construct climate
models, scientists divide
each of the Earth's
components spatially into
a set of boxes. Simple
models may have only a
few boxes. The most
complex models may have
more than a hundred
thousand.
CLIMATE MODELS HAVE TWO COMPONENTS:
1.) Earth System Models
• explore future changes in physical and biogeochemical responses to changing
atmospheric composition and radiative forcing
• use mathematical equations based on well-understood principles to depict the
behavior of Earth processes in each box.
• the movement of energy, air, and water are represented as horizontal and vertical
exchanges between the boxes. In this way, models represent interactions between
different parts of the climate system and the world.
CLIMATE MODELS HAVE TWO COMPONENTS:
2.) Integrated Assessment Models
• driving forces and responses by humans through changes in technology,
economies, lifestyle and policy
• explore alternative socio-economic conditions that would result in such future
atmospheric composition changes
• Integrated assessment models contain three main factors:
a. POPULATION
b. URBANIZATION
c. ECONOMIC DEVELOPMENT
more urban areas = more CO2
bigger economy = more CO2
more people = more CO2
EFFECT OF POPULATION SIZE ON CO2 EMISSIONS
EFFECT OF ECONOMY ON CO2 EMISSIONS
INTERNATIONAL PANEL ON CLIMATE CHANGE
(IPCC)
• international body for the assessment of climate change established by the United
Nations and World Meterological Organization in 1998
• goal is to provide the world with a clear scientific view on the current state of
knowledge in climate change and its potential environmental and socioeconomic impacts.
• thousands of
scientists from all
over the world
contribute to the
work of the IPCC
on a voluntary
basis and reflect a
range of views and
expertise
FUTURE CO2 EMISSION SCENARIOS
• very rapid economic growth
• pursue wealth over environment
• changes in economic structures
• reductions in energy use
• clean and resource-efficient
technologies.
LECTURE SUMMARY
• climate is altered by changes in radiative forcing
• carbon dioxide emitted from the burning of fossil fuel is presently the largest single
climate forcing agent
• inputs of CO2 outpace the ability of the carbon cycle to remove it from the atmosphere
• accumulation of CO2 in atmosphere exhibits a distinct seasonal trend
• CO2 and other human emissions act as greenhouse gases and contribute to the
greenhouse effect.
• greenhouse gas emission are tightly linked with economic development
• greenhouse gases emissions are expected to increase over the next century
NEXT LECTURE:
CO2 AND TEMPERATURE
MORE INFORMATION
GREENHOUSE GASES
Environmental Protection Agency
http://www.epa.gov/climatechange/ghgemissions/
TRENDS IN CO2 EMISSIONS
NOAA Earth System Research Laboratory
http://www.esrl.noaa.gov/gmd/ccgg/trends/mlo.html
IPCC AND EMISSION SCEANRIOS
http://www.ipcc.ch/