What we know about global climate change Philip Mote (206) 616-5346 [email protected]...
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Transcript of What we know about global climate change Philip Mote (206) 616-5346 [email protected]...
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 historyRecent trend: +0.5°C (0.9°F) in 30 yrs
Human influence emerges
Larsen B Ice shelfAntarctica
January 31, 2002
MODIS dataCourtesy NSIDC
February 17
February 23
March 5
Avoiding Dangerous Climate Change : Exeter Feb 2005
Antarctic Peninsula Glacier Acceleration
• “cork from bottle” analogy
• 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
• ~ 0.06mm/y global msl contribution? Work in progress
Rapid global sea level rise
11
Local evidence of warming
1928
2000
The South Cascade glacier retreated dramatically in the 20th century
Courtesy of the USGS glacier group
3.6°F2.7°F1.8°F0.9°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)
Stewart et al., 2004; Stewart et al., 2005Stewart et al., 2004; Stewart et al., 2005
Spring-pulse dates
Centers of Mass
By several measures,By several measures,Western snowfed Western snowfed
streamflow has been streamflow has been arriving earlier in the arriving earlier in the
year in recent decadesyear in recent decades
Springpulse
Center time
April 1 snowpack: no decline at high elevations
...but large declines at low elevations
Green
daily flow records dating to <1935
Metrics of flow
Center date
JJAS flow
Center date of annual flow
As observed elsewhere, mean inflow to Puget Sound is shifting earlier as the snowpack declines
Data from Climate Monitoring and Diagnostics Lab., NOAA. Data prior to 1973 from C. Keeling, Scripps Inst. Oceanogr.
Changing atmospheric composition: Changing atmospheric composition: COCO22
Mauna Loa, HawaiiMauna Loa, Hawaii
Carbon dioxide: up 32%
Natural Climate Influence Human Climate Influence
All Climate Influences
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 acidificationIntensity 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 Hurricane Catarina - first recorded South Atlantic tropical storm, March 2004Atlantic tropical storm, March 2004
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