-although the average temp. of the earth is increasing, some areas are getting warmer much faster than others while others are getting cooler
-patterns of precipitation are also predicted to change, with some areas getting wetter and some getting drier
-the frequency of extreme weather events is also predicted to increase in some areas
Historical Climate Change
-The climate of the earth has always been dynamic
-At various times in the past, the earth has been hotter or colder than it is today
-Concentrations of atmospheric gases have also varid over the millennia.
Why has the climate changed in the past
-response to natural changes in solar activity, increased volcanism, and earth's orbital characteristics.
-reduced solar activity...ice age?
-The earth is composed of a series of moving plates whose motion may influence climate change. The Permian period was a time of increased volcanic activity as supercontinent of pangea formed.
-shape of earth's orbit changes on a ~100,000 year cycle; presently, we are in a period of low eccentricity and this give us a seasonal change in solar energy
-changes in tilt of earth's axis occur on a ~41,000 year cycle
-changes in wobble of the spin axis occur on a ~23.000 year cycle
-RECENT increases in CO2 and other GHGs have changed on time scale of ~260 yrs (since Industrial Revolution)
So What's The Big Deal With Climate Change?
-in the past we weren't around to suffer the consequences
-Also, previous rate of climate change were much slower than those caused by humans today
-Organisms may not have time to adapt to the current rapid rate of climate change
fast, recent change
-we may b on our way to inadvertently recreating a mesozoic-like climate in a few generations-unfortunately our biota and ecosystems are not mesozoic
New Rates of Change
-changes in climate that previously occurred over geological time (millions of years) are now occurring in ecological time (decades)
-Newrates of climate change appear linked to human population growth and human activity
human population growth rate
..remains very high
World population growth, energy transitions, and Urbanization
-The transition to fossil fuels ushered in the industrial revolution and introduced a radically new type of society characterized by explosive population growth and urbanizaiton
-we are still today in that transition from rural agrarian to urban-industrial society
Who uses the most fossil fuels??
The US! and canada.
The carbon cycle
-fossil fuel use and land use change are adding 7.9 gigatons of carbon per year to the atmosphere
-extra 4.5 gigatons of carbon
IPCC=intergovernmental panel on climate change
a group of climate scientists from around the world who review the basic science of climate change and wrote periodic reports
--THERE have been two events that fueled climate change skeptics. There ARE uncertainties in climate science.
What gases make up the atmosphere?
argon, little carbon, more oxygen, and mostly nitrogen.
CO2 leves had remained at ~280 ppm for thousands of years, but began increasing with the Industrial Revolution and are still increasing at an unprecendented rate
traditional CO2 cycles
-co2 levels followed ice age cycles for hundreds of thousands of years: but since the industrial revolution Co2 wayy increased
fueled by the preserved detrits of long-extinct ecosystems.
drive world energy use
--hydroelectric power and such is nothing!
land use changes
increases in Co2 emissions due to fossil-fuel use and forest destruction
cutting down trees...
loss of carbon sequestration
more carbon in atmosphere
How does CO2 contribute to climate change
-GHG that traps heat radiated from earth and keep it from being lost to space
-increasing atmosphere's heat-trapping potential
Some GHG is good
-keep earth about 33 degrees celsius warmer than it would be w/o these gases
-water vapor is the most important GHG, followed by CO2 and methane.
-CFCS, ozone and benzene are also GHG.
too much GHG is bac
GHGs re-emit longwaveradiation to produce the "green house effect"
humans have causes increases in several GHGs
Co2, methane, nitrous oxide
global warming is a reality
over the last century, the average temperature has climbed about .6 degree C.
-the 1990s were the warmest decade in the past thousand years
-2007 was the second hottest year ever recorded.
climate change is complex. how doe scientists study the factors that cause climate to change?
-sophisticated computer models
-estimate emissions from smokestacks...
-they test them
is it really use
-models of global warming that include only natural drivers do a poor job at prediction. Models including human activities do a MUCH better job of prediction.
-Models suggest an increase of 5.8 degrees celsius by the year 2100.
Consequences of climate change
-melting of Arctic ice and loss of glaciers
-change sin the distributions of marine organisms
-changes in the timing of biological events
impacts of climate change
-polar regions are the best indicators of climate change
-when the ice melts, the surface of the water or land that lies beneath is darker and thus absorbs more heat from the sun. This causes a positive feedback effect and alters local climate as well as accelerated global warming.
-Albedo=the fraction of radiation striking a surface that is reflected by the surface.
Many arctic organisms
may go extinct in the wild and your grandchildren may only know them as zoo animals
It's not just the arctic
-most of the ocean is stratified by density and temperature
-global warming increased the density gradient, making it less likely for layers to mix
less mixing of water is reducing nutrients available for phytoplankton in the surface waters.
-NPP is declining
-cold-water copepods are declining in the North Atlantic
Terrestrial systems are changing too
Flowering times for some species in midwestern north america are earlier in the year
-changes in temperature and precipitin patter will change the distribution of biomass ad major oceanic habitat types, thus impacting associated fauna.
-species that disperse slowly and take a long time to grow to maturity, such as beech trees, may not be able to shift their ranges quickly enough to survive.
-humans impacts on biogeochemical cycles are among the most pressing issues of your generation
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