global climate change. our changing climate what is climate change? climate = long-term weather...

Global Climate Change

OUR CHANGING CLIMATE

What is Climate Change?

• Climate = long-term weather patterns (what you expect; weather is what you get!)

• GCC = changes in long-term pattern of atmospheric conditions involving ∆T, precipitation, storm frequency & intensity

• Global warming is one aspect

Greenhouse Effect

• Short-wave radiation absorbed by earth• Earth warms up, releases IR radiation• Tropospheric greenhouse gases (CO2, CH4, H20)

absorb IR

Greenhouse Effect

• Due to abundance, CO2 is of primary concern• Current levels at their highest in 650,000 –

2,000,000 years• Fossil fuel burning, forest clearing and burning

are the two main anthropogenic sources of increased CO2 levels

Greenhouse Gases

• Methane (from fossil fuel extraction, cattle, landfills, certain crops like rice)

• N2O from feedlots, automobiles, agriculture

• Tropospheric O3

• Halocarbons have decreased due to Montreal Protocol of 1987

• Aerosols may have short-term cooling effect

Other Factors

• Milankovitch cycles = changes in the earth’s rotation and orbit around the sun

• Solar output and solar cycle• Ocean absorption of CO2

Other Factors

El Niño = • Equatorial winds weaken and allow warm water

from western Pacific to move eastward• Prevents cold water from upwelling in eastern

PacificLa Niña =• Cold surface waters extend far westward

Other Factors

• Thermohaline circulation = worldwide current system in which warmer fresher water moves along the surface; colder, saltier water moves down

• North Atlantic Deep Water = warm surface water moves northward toward Europe; cooler water sinks and returns in other direction

STUDYING CLIMATE CHANGE

Proxy Indicators

• Preserved gas bubbles in ice• Sediment beds beneath bodies of water• Coral reefs and tree rings• All are forms of indirect evidence

Atmospheric Sampling

• Started in 1958 – Charles Keeling of Scripps Institution of Oceanography – trends of CO2 concentrations

• His data showed shows an increase of CO2 concentrations from 315 to 383 ppm

Modeling

• Coupled general circulation models (CGCMs)• Combine what is known about weather

patterns, atmospheric circulation, atmosphere-ocean interactions, and feedback mechanisms to simulate climate processes

• Over a dozen research labs world wide• A good approximation of relative effects of

natural and anthropogenic influences

CURRENT & FUTURE IMPACTS

IPCC Report

2007 – summarized 1000s of reportsIncludes trends in sfc temp, rainfall patterns, snow

& ice cover, sea levels, storm intensity, etcIncluded a series of possible climate change

scenarios, including:• Temp increases (1.33oF in last century)• Increases in power and duration of storms• Changes in precipitation

Muir Glacier: 1948 and Now

IPCC Report

• Polar ice melt• Glaciers disappearing (Since 1980 – glaciers

have lost an average of 9.6 m vertical• This changes earth’s albedo• Rising sea levels (3.1 mm/y from 1993 – 2003)• A several inch vertical rise = many feet of

horizontal incursion into coastal lands

IPCC Report

• Storm surges present a great risk to island nations

• Rising sea levels will force people to choose between relocating or investing in costly protections

• Ecosystems also affected• Timing of seasonal events are creating complex

effects in ecosystems

IPCC Report

Societal impacts will also occur• Agriculture – cuts in productivity (drought &

flood)• Forestry – insects, disease outbreaks, , invasive

species, fires• Health – heat stress, tropical diseases,

respiratory ailments, hunger• Economics – est. of 1 – 5% of GDP

RESPONDING TO CLIMATE CHANGE

Our Response

Mitigation or adaptation?• Mitigation = actions that would reduce

emissions of GHG• Adaptation = search for ways to soften the blow

(building sea walls is an ex.)• Electricity generation is largest source of GHG in

US• Conservation & efficiency

Our Response

• Natural gas has less impact• Carbon sequestration would allow current

practices to continue• Transportation is 2nd largest source• Cars are highly inefficient (15%)• Alternative engines, driving less, public

transportation are possibilities

Our Response

• Sustainable agriculture & land management• Reduce methane emissions from rice fields,

cattle• Preserving forests; increase reforestation• Recovering methane from landfills, treating

wastewater, energy from solid waste

Our Response

Kyoto Protocol• Began as the UN Framework Convention on

Climate Change• Binding international treaty to reduce GHG

emissions (US refused to sign)• In the 10 years after Rio conference (1992) – US

increased GHG by 13%; Germany & UK decreased by 13 – 18%

Our Response

• Market mechanics – cap and trade• A carbon offset represents a reduction in

emissions somewhere else - like a renewable energy or a reforestation project - to balance out the emissions you cannot reduce.

• Reduce your own carbon footprint

OZONE DEPLETION

•UVA: λ = 320-400nmCauses tanning•UVB: 290-320nm; burns, skin cancer•UVC: 10-290nm formation of ozone

Research

CFCs are persistent in the atmosphere• Rise into the stratosphere over 11-20

years• Break down under high-energy UV

radiation–Halogens produced accelerate the

breakdown of O3 to O2

• Each CFC molecule can last 65-385 years

Reducing Effects

• Stop producing all ozone-depleting chemicals

• 60–100 years of recovery of the O3 layer• 1987: Montreal Protocol; 1992:

Copenhagen Protocol• Ozone protocols: prevention is the key• Substitutes for CFCs are available

Conclusion

• Many factors, including human activities, can shape atmospheric composition and global climate.

• Scientists and policymakers are beginning to understand anthropogenic climate change and its environmental impacts more fully.

• Reducing greenhouse gas emissions and taking other actions to mitigate and adapt to climate change represents the foremost challenge for our society in the coming years.