BIOL 3999: Issues in Biological Science

BIOL 3999: Issues in Biological Science

GLOBAL CHANGE BIOLOGY

Dr. Tyler EvansEmail: [email protected]: 510-885-3475Office Hours: M,W 10:30-12:00 or by appointmentWebsite: http://evanslabcsueb.weebly.com/

mailto:[email protected]

PREVIOUS LECTURE• How human systems influence Earth systems

• socio-economic development

• production and consumption

• resource use

• ecosystems• climate• geochemical

cycles

HUMAN SYSTEMSEARTH SYSTEMS

Global ChangeBiology

HOW ARE HUMANS INFLUENCING EARTH SYSTEMS?

ALTERING CLIMATECLIMATE: 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 outputNEGATIVE

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.

• Prior to the industrial revolution, the carbon cycle was approximately in balance.

SOURCES (add CO2)• respiration

SINKS (removes CO2)• photosynthesis

• oceans

CO2CO2

• 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).

• 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

SOURCES (add CO2)• respiration• fossil fuels

SINKS (removes CO2)• photosynthesis

• oceans

CO2CO2

A USEFUL ANALOGY

CO2 IS ACCUMULATING IN THE ATMOSPHERE

393 ppm in 2013

315 ppm in 1958

CO2 IS ACCUMULATING IN THE ATMOSPHERE

• 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

KEELING CURVE

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

resp

iration

photosynthesis

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?

• 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

equator

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.


• 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.


• 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.


• 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.


• 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 AGRICULTURE LANDFILLS

• primary source of methane is natural gas

• 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 NYLONNITRIC ACID CARS

BURNING ORGANIC MATTER

improve plant production

also used in fertilizers formed in catalytic converters

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 TIMECARBON DIOXIDE

GREENHOUSE GASES THROUGH TIMEMETHANE

GREENHOUSE GASES THROUGH TIMENITROUS OXIDE

GREENHOUSE GASES THROUGH TIMESULFUR 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 SCENARIOSPredictions focus on carbon dioxide:• other greenhouse gases track the pattern of CO2• CO2 is by far the largest source of greenhouse gases

A CO2 PROBLEMU.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

• 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.

FUTURE CLIMATE MODELS

• 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.

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:

CLIMATE MODELS HAVE TWO COMPONENTS:

a. POPULATION b. URBANIZATION c. ECONOMIC DEVELOPMENT

more people = more CO2

more urban areas = more CO2bigger economy = 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 socio-economic 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

http://www.esrl.noaa.gov/gmd/ccgg/trends/mlo.htmlNOAA Earth System Research Laboratory

MORE INFORMATION

http://www.ipcc.ch/

TRENDS IN CO2 EMISSIONS

IPCC AND EMISSION SCEANRIOS

GREENHOUSE GASES

http://www.epa.gov/climatechange/ghgemissions/Environmental Protection Agency

Documents

BIOL 3999: Issues in Biological Science