an inconvenient truth for handouts

An Inconvenient Truth Discussion

www.WeatherOutreach.org

Get Fuzzy by Darby Conley


Summary and Comments

Global Climate Change• There is no longer any

scientific doubt that the Earth’s average surface temperature is increasing

– 1.3°F in last century

– Recent decades warmer than any comparable period in last 400 years (possibly much longer)

• Ocean temperature, ice and snow cover, and sea level changes consistent with this global warming– Sea level up 7 inches in 20th century

Causes of Recent Climate Change• There is very high confidence that

human-generated increases in greenhouse gas concentrations are responsible for most of the global warming observed during the past 50 years

• It is very unlikely that natural climate variations alone, such as changes in the brightness of the sun, have produced this recent warming

Invasive species, disease and global warming

• Invasive species due to land use change and importation

• Not sure how invasive plants and insects will respond

Reference: CO2 changes during the ice ages

• A full understanding of why CO2 changes in precisely the pattern that it does during ice ages is elusive, but among the most plausible explanations is that increased received solar radiation in the southern hemisphere due to changes in Earth's orbital geometry warms the southern ocean, releasing CO2 into the atmosphere, which then leads to further warming through an enhanced greenhouse effect.


The Greenhouse Effect

CO2 and Temperature connections in the ice core

record• Observed long-term relationship

between CO2 and temperature in Antarctica supports our understanding of the warming impact of increased CO2 concentrations

• Moreover, our knowledge of why CO2 is changing now (fossil fuel burning) is solid.

• Carbon cycle – CO2 is a greenhouse gas– Carbon cycle feedback is positive

(increasing temps lead to increasing CO2 and CH4)

– Future changes in CO2 will be larger than we might anticipate.

Climate impacts on the ocean conveyor

• Timing is uncertain. • Younger Dryas 11,000 y.a.

– A large discharge of fresh water into the North Atlantic disrupted currents, causing significant regional cooling.

• IPCC predicts a slowdown in the circulation ~ 30% by 2100– Circulation modeling and

future inputs of melted ice -not well understood.

– Few scientists are willing to completely rule out the possibility of a more substantial change in the future.

Ice-sheet driven sea level rise

• Gore correctly asserted that melting of Greenland or the West Antarctic ice sheet would raise sea levels 20ft (6 meters). – No time frame, very uncertain– 20 ft

• about how much higher sea level was around 125,000 years ago during the last inter-glacial period.

– Then, global temperatures were only a degree or two warmer than today

Impact of sea ice retreat on Polar bears

• Summer Arctic sea ice shattered all records this year for the minimum extent.

• Polar bears – depend on the sea ice

• hunt for seals in the spring and summer

– disappearance ice • likely to impact them severely

– Studying the regional populations of polar bears is not easy and assessing their prospects is tough.

• Arctic ecosystems are changing on many different levels. – It may be the smaller and less

photogenic elements that have the biggest impact. –RealClimate.org

Impact of sea ice retreat on Polar bears

• Summer Arctic sea ice shattered all records this year for the minimum extent. – This was partially related to wind patterns favorable to ice export in the

spring, but the long term trends are almost certainly related to the ongoing and dramatic warming in the Arctic.

• Polar bears do indeed depend on the sea ice to hunt for seals in the spring and summer, and so a disappearance of this ice is likely to impact them severely.

• The specific anecdote referred to in the movie came from observations of anomalous drownings of bears in 2004 and so was accurate.

• However, studying the regional populations of polar bears is not easy and assessing their prospects is tough. – In the best observed populations such as in western Hudson Bay (

Stirling and Parkinson, 2006), female polar bear weight is going down as the sea ice retreats over the last 25 years, and the FWS is considering an endangered species listing.

– However, it should be stated that in most of the discussions about polar bears, they are used as a representative species.

• Take home message: Arctic ecosystems are changing on many different levels. In the end, it may be the smaller and less photogenic elements that have the biggest impact.

http://nsidc.org/news/press/2007_seaiceminimum/20071001_pressrelease.html

http://www.springerlink.com/content/p235r60mu4878820/

http://neptune.gsfc.nasa.gov/publications/pdf/pubs2006/Stirling%20-%20Possible%20Effects%20of%20Climate%20Warming.pdf

http://www.biologicaldiversity.org/swcbd/species/polarbear/Proposed-Rule.pdf

Pacific island nations needing to evacuate

• Much of Tuvalu – is only a few feet above sea

level– With more sea level rise

• increasing brine in groundwater• increasing damage and coastal

erosion from tides and storm surges

• Government of Tuvalu asked New Zealand to be ready to evacuate islanders

• In the movie: "That's why the citizens of these pacific nations have all had to evacuate to New Zealand“.

Kilimanjaro• Ongoing discussion in the

literature:– Is retreat of ice on Kilimanjaro

related to the direct effects of climate change? • warming atmospheric

temperatures– Or indirect effects of climate

change• altered patterns of humidity,

cloud cover, and precipitation influencing Kilimanjaro's ice mass

• Take home message– (a) ice field that we know has

existed for at least the past 12,000 years is shrinking

– (b) most of the other glaciers are disappearing as well.

Feb 1993

Feb 2000

http://earthobservatory.nasa.gov/Newsroom/NewImages/Images/kilimanjaro_etm_93_00.jpg

Drying up of Lake Chad

• Extremes– Droughts– Flooding

• Lake Chad Change – reduction of rainfall across entire Sahel from 1950s

to 1980s– rainfall today still substantially below high point 50

years ago– Other factors

• Irrigation and upstream water use. • Substantial evidence that at least a portion of this drying

out is human-caused. • Indian Ocean changes in sea surface temperature• Increase in atmospheric aerosols in the Northern

hemisphere.

http://www.dailymail.co.uk/pages/live/articles/news/worldnews.html?in_article_id=479576&in_page_id=1811

Drying up of Lake Chad• Gore uses this example to illustrate that there

are droughts in some regions even while other areas are flooding.

• Unfortunately this is what models suggest. • The dominant cause

– reduction of rainfall across entire Sahel from 1950s to 1980s

– rainfall today still substantially below high point 50 years ago

– Other factors• Irrigation and upstream water use. • Substantial evidence that at least a portion of this drying

out is human-caused. • Indian Ocean changes in sea surface temperature• Increase in atmospheric aerosols in the Northern

hemisphere.

Hurricane Katrina and global warming

• Katrina is used– Destructive power of hurricanes– Cope with natural disaster– Ex. of what could get worse in a

warmer world. • Nowhere does Gore state that

Katrina was caused by global warming. – Individual hurricanes cannot be

attributed to global warming, but the statistics of hurricanes, in particular the maximum intensities attained by storms, may be.

http://geology.com/news/images/hurricane-katrina-satellite-image.jpg

Impact of ocean warming on coral reefs

• Stress Factors– Overfishing– deliberate destruction– water pollution– sea level rise– ocean acidification – warming oceans. – That rising temperatures and other factors cause coral

bleaching is true. • Bleaching episodes happen when the coral is

under stress, and many examples have been linked to anomalously warm ocean temperatures

http://web.syr.edu/~tjconena/coral_reefs.htm

What process could most likely change the climate?

Warmer climate More evaporation at the equator

More moisture in the air

More moisture can be held in the air

More rain at higher latitudesMore freshwater

in the ocean

Ocean is not as salty and dense

Water does not sink in the northern latitudes

Circulation slows down

and changes

Melting Glaciers


Can giant hurricanes exist all around the world like in the Day After Tomorrow?

• Clusters of thunderstorms cannot merge together to form a continent-scale blizzard with a calm eye over land.

• Huge storms with calm eyes happen over the oceans not over land. – Hurricanes or Tropical Storms

• Require that the core of the storm be over warm ocean water

Photo: earthobservatory.nasa.gov/NaturalHazards/Arch...

Three Glaciers Retreating

• Source: C.L. Andrews. 1912, 1938. Denver Glacier: From the Glacier Photograph Collection . Boulder, CO: National Snow and Ice Data Center. Digital Media; Marion T. Millett. 1958. Denver Glacier: From the Glacier Photograph Collection . Boulder, CO: National Snow and Ice Data Center. Digital Media.

Denver Glacier in Recession, Alaska, British Columbia

1912

1938

http://nsidc.org/data/g00472.html

http://nsidc.org/data/g00472.html

Temperature Analysis

• “Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level” (IPCC report 2007).


Contributions to Sea Level Rise


Long-term Changes in Climate• Long-term changes are observed at:

– Continental Scales– Regional Scales– Ocean basin Scales

• These changes include:– Changes in Arctic temperatures and ice– Widespread changes in precipitation

amounts– Ocean salinity– Wind patterns – Aspects of extreme weather

• Droughts• Heavy precipitation• Heat waves• Intensity of tropical cyclones

- 2007 IPCC report

What can change our climate?• Changes in these factors alter the

energy balance of the climate system:– Solar radiation– Land surface properties– The atmospheric abundance of

greenhouse gases and aerosols


How do we know that this is not a normal cycle?

We use past climate data and compare influencing factors.


How do we know about past climates?

• Tree Rings – Growth is controlled by temperature, precipitation and sunlight

• Pollens – give a good indication of what was living at the time indicating a temperature range

• Ice and sea bed cores – Gasses in bubbles, dust, isotopes, accumulation rate

• The fossil record • Coral beds

Note: Uncertainties generally increase with time into the past due to increasingly limited spatial coverage.


What has Changed and what has Not Changed?


Aspects of climate that have NOT changed

• Day night temperature differences have remained constant. Both the maximum and minimum temperatures have increased at the same rate. The trends are highly variable from one region to another.

• Antarctic sea ice extent continues to show inter-annual variability and localized changes but no statistically significant average trends, consistent with the lack of warming reflected in atmospheric temperatures averaged across the region.

• There is insufficient evidence to determine whether trends exist in– Meridional overturning circulation of the global ocean– Small scale phenomena

• Tornadoes• Hail• Lightning • Dust-storms


Ward Hunt Ice Shelf, 2002

Consequences of Climate Change


Muir Inlet, Alaska

National Snow and Ice data centerhttp://nsidc.org/cgi-bin/gpd_run_pairs.pl

2004

1941

Glacier Bay National Park and Preserve

Larsen B ice shelf, Antarcticaca. 100 x 80 miles

Mar. 5, 2002Feb. 17, 2002

Larsen B ice shelf,Antarctica


Arctic Polar Ice Cap

• Since 1979, the size of the summer polar ice cap has shrunk more than 20 percent.

• On Sept. 21, 2005, sea ice extent dropped to 2.05 million sq. miles, the lowest extent yet recorded in the satellite record.

• This loss is twice the size of Texas.

1979

http://www.nasa.gov/centers/goddard/news/topstory/2003/1023esuice.html

2003


NASA


Priority Actions for Consumers• Vote!• Transportation

– Choose a place to live that reduces the need to drive.

– Think twice before purchasing another car.

– Choose a fuel efficient, low polluting car.

– Set concrete goals for reducing your travel.

– Whenever practical walk, bicycle or take public transportation

– Brower, 1999


Priority Actions for Consumers

• Food– Eat less meat.– Buy certified organic produce.

• Household Operations– Choose your home carefully.– Reduce the environmental costs of heating and hot water. – Install efficient lighting and appliances– Choose an electricity supplier offering

renewable energy.• Policy

– Vote, write letters, attend rallies, call your representatives and express your views.

– Brower, 1999

Thank you!

an inconvenient truth for handouts

Documents