Global Climate Change: What the Future
Holds, and What We Can Do About It
Dr. David Karowe
Professor, Department of Biological Sciences
Schedule of Topics
September 29: Recent climate change (Dave Karowe)
1
October 6: Future climate change (Dave Karowe)
October 13: Effects of climate change on plants and
animals (Dave Karowe)
current
future
2
October 20: Effects of climate change on aquatic
ecosystems (Chuck Ide)
October 27: Effects of climate change on human health
(Dave Karowe)
3
November 3: Economics of climate change (Dave Karowe)
Skeptics arguments (Dave Karowe)
November 10: Biofuels, carbon capture and storage
(Steve Bertman and Dave Barnes)
4
November 17: Wind, solar, and personal behaviors
(John Patten and Dave Karowe)
Earth’s climate has always changed
Over the last billion years:
- but most or all large changes (≥2o C) have taken
hundreds of thousands or millions of years
5
Very good temperature data exist for the past
800,000 years:
~ 100,000 yr glacial/interglacial cycles
Data come from ice cores with annual rings
18O/16O
6
What has caused climate to change over the last
800,000 years?
Long-term climate change due to cyclic changes in
Earth's orbit, tilt, and precession of the equinoxes
(Milankovitch cycles)
Orbital eccentricity:
~100,000 years
Axial tilt:
~41,000 years
Precession:
~26,000 years
7
What’s happened over the last 21,000 years?
www.youtube.com/watch?v=C3Jwnp-Z3yE&hd=1
The future projection is based on the assumption of
complete cessation of carbon dioxide emissions in 2100
(~IPCC A2). Because future world population is
uncertain, it was frozen at 7 billion people.
What was North America like the last time
Earth was ~ 5o C cooler?
- Michigan was covered by
almost a mile of ice
19,000 BC
8
What’s been happening over the last 1,500 years?
modern
warming
Little Ice Age
- tree ring and thermometer records indicate
two anomalous periods since 500 AD
Little Ice Age due to temporary reduction in solar output
~1o C cooling of Northern Hemisphere 1550-1850
Maunder minimum
9
What’s been happening over the last 130 years?
modern
warming
Temperature Change (oC)
Since 1880, Earth has warmed ~ 0.8o C
10 warmest years in history:
2010, 2005, 2007, 2009, 1998*,
2007, 2002, 2003, 2004, and 2008
10
Temperature difference relative to 1950-1980
http://data.giss.nasa.gov/gistemp/animations/
Rate of global warming has been increasing
- global rate over land since 1979 is 5 times faster
than since 1850
1850-2005
1979-2005
Global
Land
Ocean
0.054
0.039
0.244
0.134
Northern Hemi.
Land
Ocean
0.063
0.040
0.317
0.188
Southern Hemi.
Land
Ocean
0.036
0.038
0.127
0.091
- land is warming faster than the ocean
- Northern Hemisphere is warming faster than Southern
11
Since 1900, greatest warming in northern North
America, Asian interior, and southeastern Brazil
In Western Hemisphere, greatest warming in winter;
in Eastern Hemisphere, greatest warming in spring
- but warming has occurred in all seasons
12
Since 1979, Michigan has warmed by ~0.75 oC
Antarctic
peninsula
Arctic
Temperature relative the 1951-1980 mean
- pronounced latitudinal pattern to recent warming
Did 2010 feel like a particularly warm year?
- Michigan was ~0.75o C above the 1951-1980 mean
Temperature relative the 1951-1980 mean
13
Last summer was Michigan’s 6th warmest on record
This summer was Michigan’s 18th warmest on record
14
Since 1900, no consistent trend in total
global precipitation
But heavy precipitation events now account for a
higher percent of total precipitation
15
Severe storms cause flooding, erosion, disease
Flooding has increased globally in the last 50 years
16
In the U.S., severe rainstorms are now more common
- 20% increase in Michigan since 1948
- 50% increase in southwest Michigan
This year, Michigan had its 2nd wettest spring on record
17
As a result, Michigan experienced flooding this spring
… but Ohio had it worse…
18
And there was extensive flooding along Mississippi
Tunica, Mississippi
Droughts have also increased, especially since 1950
- droughts are more widespread because of warming
since 1950
19
Since 1950, global land surface area in “severe” or
“extreme” drought increased from 13% to 30%
Currently, 43% of U.S. is in drought
18%
35% 66%
85%
Exceptional Drought:
PDSI <- 5.0 or <5% of normal rainfall
20
Currently, 7% of Michigan is in drought
- another 29% is
abnormally dry
September 20
As a result, the cryosphere has been melting
- ice sheets, ice shelves, sea ice, glaciers, ice caps,
frozen ground (permafrost)
- any melting produces a positive feedback
by reduced albedo (reflectivity)
21
Arctic summer sea ice extent (area) has been decreasing by
up to 10% per decade
http://nsidc.org/sotc/sea_ice_animation.html
- record low in 2007
- thickness has decreased by >40% since 1960
Glaciers have been retreating worldwide
1978
2000
- ice loss from 30 ‘reference’ glaciers from 1996-2005 was twice
as fast as the previous decade, and four times as fast as the
decade before that (1976-1985)
22
Recently, 97% of Earth’s glaciers have been retreating
Red = retreating
Blue - advancing
Seasonal snowcover has also been decreasing
- mean winter maximum of 33% of Earth’s land surface,
~98% in the Northern Hemisphere
- so biggest albedo effect
- earlier spring snowmelt in western U.S.
- effects on soil moisture
23
Greenland ice sheet is melting at an accelerating rate
- meltwater also accelerates ice slippage into ocean
Antarctic ice shelves are shattering
- recent collapse of Wilkins Ice Shelf
24
Lake and river ice are also decreasing
- since 1850, for NH lakes and rivers, spring ice breakup is
~9 days earlier, and autumn freeze-up is ~10 days later
Freeze dates
ice cover has decreased by
~4 weeks for Grand
Traverse Bay
Breakup dates
Permafrost is warming and, to a small extent, melting
~25% of NH land mass is underlain by permafrost
- thickness of active layer has increased by ~10-30 cm since
mid-1990s in many sites
25
Warming is detectable to ~40 meters in many places
Can climate change be due to “natural variation”?
Since 1900, energy increase from greenhouse gasses
is about 20 times energy increase from the sun
26
Since 1900, energy increase from greenhouse gasses
is about 20 times energy increase from the sun
GHG added
~ 2.98 W/m2
aerosols removed
~ -1.4 W/m2
the sun added
~ 0.12 W/m2
- aerosols have masked ~40% of the GHG warming
Solar Irradiance
During the current time of most rapid warming (the
last 30 years), solar irradiance has been decreasing
27
Finally, models do a good job of replicating past
climate change only if they use anthropogenic forcings
“natural variation” would most likely have caused a
slight cooling since 1900
So what’s really causing current warming?
Greenhouse gasses
GHGs let visible
wavelengths
pass, but absorb
and re-radiate
IR (heat)
Some greenhouse
effect is necessary
for life on Earth
28
The carbon cycle is out of balance
Net: +4 bty
+2 bty
-3 bty
+8 bty
-3 bty
Increased greenhouse gas (GHG) concentrations
- CO2 increased from 280 ppm < 1850 to >390 ppm today
- CO2 accounts for ~60% of GHG warming
- methane, nitrous oxide, CFCs, ozone cause the rest
29
U.S. probably emits more carbon than any other
major country
Midwest would be 4th highest emitting country
Countries proportional to their 2000 emissions
30
U.S. also emits the most carbon per capita
Residential and transportation sectors account for
about half of US energy consumption
(~80% heating
and appliances)
(~80% cars and
trucks)
31
85% of US energy use comes from fossil fuels
Hydropower
Biomass
Geothermal
Wind
Solar
2.4%
3.6%
0.3%
0.3%
0.08%
Land use change (mostly deforestation) is also a major
contributor to increased GHG levels
- accounts for 20-25% of CO2 added to the atmosphere
32
Best estimate: ~95% of current warming is
due to human activities
Greenhouse gas emissions
Deforestation
33