Global and Regional Global and Regional Climate ChangeClimate Change

Part 2Part 2

during the 20during the 20thth and 21 and 21stst centuriescenturies

January 18, 2011January 18, 2011ENVIR/SMA/ATMS/ESS585ENVIR/SMA/ATMS/ESS585

Amy Snover, ATMS 585 2003

Are these regional changes due to anthropogenic climate

change?

• At the scale of the western US, partly

– “[35-60%] of the climate related trends of river flow, winter air temperature, and snow pack between 1950-1999 are human-induced.”• Based on two different GCM simulations,

and for one of those two different downscaling approaches

Barnett et al. 2008. Human-induced changes in the hydrology of the western United States. Science Express Reports 10.1126/science.1152538.

Outline

• Assessments of global climate change

• The greenhouse effect

• Past changes

• Projected future changes

How much Carbon Dioxide will be released into the

atmosphere?

A1B

A2 (business as usual)

B1 (utopia)

Estimates depend on population and economic projections, future choices for energy, governance/policy options in development (e.g., regional vs. global governance)

A1B

A2

B1

COCO22 Emissions Emissions COCO22 Concentrations Concentrations

A1FI

A1FI

Raupach et al 2007, PNAS (updated)

Recent emissions have been near the upper end of Recent emissions have been near the upper end of the most intense (A1FI) fossil fuel scenario the most intense (A1FI) fossil fuel scenario established by the IPCC’s 2000 special report on established by the IPCC’s 2000 special report on emissions scenariosemissions scenarios

A1FI

now

Actual CO2 emissions

From realclimate.org

Karl & Trenberth 2003

The full range (~1.5˚ to 6˚C) of projected temperature increases represents a combination of emissions and model uncertainties

+6˚C

+1.5˚C

We are in the early stages of an era of We are in the early stages of an era of rapid climate and environmental changerapid climate and environmental change

A1B is a typical “business as usual” (2090-2099) scenario: Global mean warming 2.8oC; Much of land area warms by ~3.5oC

Arctic warms by ~7oC; get less warming for lower GG concentrations

Projections of Future Changes in Climate

Drying in much of the subtropics, more rain in higher latitudes and in the wet tropics, continuing the broad pattern of rainfall changes already observed.

21st Century PNW Temperature and Precipitation Change Scenarios

• Projected changes in temperature are large compared to historic variability

• Changes in annual precipitation are generally small compared to past variations, but some models show large seasonal changes (wetter autumns and winters and drier summers)

21st century PNW climate scenarios relative to past variability

Coasts

• Global SLR: 7-23” by 2100

• Medium estimates of SLR for 2100:+2” for the Olympic Peninsula +11” for the central coast+13” for Puget Sound

• Higher estimates (up to 4 feet by 2100 in Puget Sound) cannot be ruled out at this time.

Rising sea levels will increase the risk of flooding, erosion, and habitat loss along much of Washington’s 2,500 miles of coastline.

3”

6”

30”

50”

2050 2100

13”

40”

20”

10”

6”

Projected sea level rise (SLR) in Washington’s waters relative to 1980-1999, in inches. Shading roughly indicates likelihood. The 6” and 13” marks are the SLR projections for the Puget Sound region and effectively also for the central and southern WA coast (2050: +5”, 2100: +11”).

Extreme Events

*Judgmental estimates of confidence by IPCC: very likely - 90-99% chance,likely - 66-90% chance. Source: IPCC SPM 2007

Sources of Uncertainty

1. Future greenhouse gas and aerosol emissions are especially important for the 2nd half of the 21st Century

2. Different climate models respond in different ways to the same forcing - a consequence of imperfect knowledge and modeling of geophysical processes

3. Different downscaling approaches lead to different local/regional outcomes from the same global climate model climate projection

Climate change and natural variations

• Climate change may be manifest partly as a change in the relative frequency of natural variations (e.g., El Niños vs. La Niñas)

• Likely changes very uncertain

– It currently isn’t clear if ENSO will be stronger, weaker, or unchanged in a warmer future! (see Collins et al 2010, Nature Geosciences)

Climate change and ENSO

Trend-ENSO pattern correlation

Rati

o o

f EN

SO

vari

abili

ty

La Niña-like El Niño-like

vari

abili

ty v

ari

abili

ty incr

. incr

. d

ecr

. d

ecr

.

• Most climate Most climate models project a models project a background trend to background trend to El Niño-like El Niño-like conditions in the conditions in the tropical Pacifictropical Pacific

• They also tend They also tend to show weaker to show weaker teleconnections teleconnections to N. Pacific to N. Pacific climateclimate

• climate models do climate models do not show systematic not show systematic changes in ENSO changes in ENSO activity activity

IPCC WG1 2007

Projected changes in the amplitude of ENSO variability

• the “best” climate models for simulating ENSO show no clear change in ENSO variance as a consequence of increased greenhouse forcing - Collins et al 2010, Nat Geosci

The future will not present itself in a The future will not present itself in a simple, predictable way, as natural simple, predictable way, as natural variations will still be important for variations will still be important for

climate change in any location climate change in any location

Overland and Wang Eos Transactions (2007)

Box1

oC

Deg

rees

C

Downscaling Relates the “Large” to the “Small”

~200 km(~125 mi)resolution

~5 km(~3 mi)

resolution

Downscaling and Regional Climate Modeling

Global ClimateModel

Regional Climate Model (WRF)

Statistical Downscaling

(BCSD)

Bias CorrectionStat Downscale

6-hourlyMonthly

Time Disaggregation

HourlyOutput

DailyOutput

100-200 km

12-50 km~7-32 mi

6 km~3.7 mi

Statistical Downscaling • Maps the climate change signal from a global model onto the observed patterns• Computationally efficient• Can tune to observed climate• Preserves uncertainty in Global Climate Models• Cannot represent fine-scale patterns of climate change

Regional Climate Models (“Dynamic Downscaling”) • Extend the physical modeling of the climate system to finer spatial scales• Computationally demanding• Cannot correct bias in global model• Adds to uncertainty from Global Climate Models

150-km GCM

High resolution is needed for regional studies

Washington

Oregon

IdahoC

asca

de R

ange

Rocky M

ountains

Snake Plain

Olympics

• Global Models Typically have 100-200 km resolution

• Cannot distinguish Eastern WA from Western WA• No Cascades• No Land cover differences

150-km GCM

High resolution is needed for regional studies

Washington

Oregon

IdahoC

asca

de R

ange

Rocky M

ountains

Snake Plain

Olympics

• Global Models Typically have 100-200 km resolution

• Cannot distinguish Eastern WA from Western WA• No Cascades• No Land cover differences

• Regional Models Typically have 12-50 km ( resolution

• 12 km WRF at UW/CIG• Can represent major topographic features• Can simulate small extreme weather systems• Represent land surface effects at local scales

12-km WRF

Why do we want to simulate the regional climate?

Process studies Topographic effects on temperature and precipitation Extreme weather Attribution of observed climate change Land-atmosphere interactions

Climate Impacts Applications Streamflow and flood statistics Water supply Ecosystems Human health Air Quality

Regional Climate Modeling at CIG WRF Model (NOAH LSM) 12 to 36 km (~7 - 32 mi)

ECHAM5 forcing CCSM3 forcing (A1B and A2 scenarios)

HadRM 25 km (~15 mi) HadCM3 forcing

Statistical Downscaling CCSM3

Fall Difference between 1990s and 2040s

Low spatial detail for climate change signal°C %

Temperature Precipitation (%change)

WRF “Dynamic Downscaling” CCSM3

Temperature Precipitation (%change)

Fall Difference between 1990s and 2040s

High spatial detail for climate change signal%

Land-Atmosphere Interactions

Snow Cover Change Temperature Change

Change in Winter Temperature (degrees C)Change in fraction of days with snow cover

Wintertime Change from 1990s to 2050s

Salathé et al 2008

Land-Atmosphere InteractionsWintertime Change from 1990s to 2050s

Salathé et al 2008

Solar Radiation