What we know about global climate change

Philip Mote (206) 616-5346 philip@atmos.washington.edu

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