Transcript What We Know About Global Climate Change

What we know about global climate
change
Philip Mote (206) 616-5346
[email protected]
University of Washington
What we know (high
confidence)
• Earth’s climate is changing
• Humans are involved and the pattern is
unlike natural changes
• Global average temperature is likely to
increase 1.4-5.8°C this century, most
land areas more
• We know this through peer-reviewed
research and assessments
Evidence of warming
•
•
•
•
•
Direct measurements
Glaciers receding
Ice shelves collapsing
Snow declining and streamflow shifting
Shifts in ranges and behavior of species
Understanding recent climate history
Recent trend:
+0.5°C (0.9°F)
in 30 yrs
Human influence
emerges
Larsen B
Ice shelf
Antarctica
January 31, 2002
MODIS data
Courtesy NSIDC
February 17
February 23
March 5
Antarctic Peninsula Glacier
Acceleration
• Larsen A – x3 increase in flow
speed of 2 feed glaciers
• Larsen B – x2-x6 increase in
flow speed of 4 feed glaciers
• Hektoria glacier lowered by
~40m in 6 mo
• Glaciers south of collapse region
unaffected
• “cork from bottle” analogy
• ~ 0.06mm/y global msl
contribution? Work in progress
Avoiding Dangerous Climate Change :
Exeter Feb 2005
0.3
Satellite temperature
trends
Temperature Trends (K/decade)
(a)
UAH: T_2
0.25
RSS: T_2
0.2
Surface Temp. (4, 5)
0.15
0.1
0.05
0
-0.05
1979-2001
-0.1
Globe
NH
SH
Tropics
0.3
Temperature Trends (K/decade)
(b)
UAH: T_850-300
0.25
RSS: T_850-300
0.2
Surface Temp. (4, 5)
0.15
0.1
0.05
0
-0.05
1979-2001
-0.1
Globe
NH
SH
Tropics
Fu et al. (2004)
11
Rapid global sea level rise
Local evidence of warming
13
The South Cascade
glacier retreated
dramatically in the
20th century
1928
Courtesy of the USGS
glacier group
2000
3.6°F
2.7°F
1.8°F
0.9°F
Puget Sound
area
Race Rocks lighthouse,
Victoria
As the West warms,
winter flows rise and
summer flows drop
Figure by Iris Stewart,
Scripps Inst. of Oceanog.
(UC San Diego)
By several measures,
Western snowfed
streamflow has been
arriving earlier in the
year in recent decades
Spring-pulse dates
Center
time
Spring
pulse
Centers of Mass
Stewart et al., 2004; Stewart et al., 2005
April 1 snowpack: no decline at high elevations
...but large declines at low elevations
daily flow records dating to <1935
Green
Metrics of flow
Center date
JJAS flow
As observed elsewhere, mean inflow
to Puget Sound is shifting earlier as
the snowpack declines
Center date of annual flow
Causes of climate change
Changing atmospheric composition: CO2
Mauna Loa, Hawaii
Data from Climate Monitoring and Diagnostics Lab., NOAA.
Data prior to 1973 from C. Keeling, Scripps Inst. Oceanogr.
Carbon dioxide: up 32%
Natural Climate Influence
Human Climate Influence
All Climate Influences
Future climate change
21st century temperature change
IPCC (www.ipcc.ch)
Climate change commitment:
at any point in time, we are
committed to additional
warming and sea level rise
from the radiative forcing
already in the system: the
brakes work slowly!
(Meehl et al., 2005: How much more
warming and sea level rise? Science,
307, 1769—1772)
Recent findings and events
Ocean acidification
Intensity and destructiveness of tropical
cyclones may be increasing (controversial)
Unprecedented 2003 European heat wave may
have been accentuated by warming
Hurricane Catarina - first recorded South
Atlantic tropical storm, March 2004
Heat-wave deaths in France, August 2003
(SINERM 2003)
The 2005 Atlantic hurricane season
Total: 27 (vs 21 in 1933)
Total: 13 (vs 12 in 1969)
Conclusions
Human influence on climate has emerged
Warming and its consequences will continue
even after greenhouse gas concentrations are
stabilized
