Climate Variability, Change and Extreme Events NCAR Earth System Laboratory National Center for Atmospheric Research NCAR is Sponsored by NSF and Partial support was provided by the Willis Research Network, the Department of Energy, and the Offshore Energy Industry Greg Holland 1

Summary Short Background on Climate Variability and Change; Impact on Extremes – Tipping Points – Extreme Weather General Impact Droughts and Flooding Rains Hurricanes 2 Holland, Cherry Creek Science Teachers Nov 2010

Fueling the Weather and Climate 3 Holland, Cherry Creek Science Teachers Nov 2010 Incoming Shortwave (UV and Visible) Reflected Shortwave Outgoing Longwave Heat Radiation With no atmosphere the equilibrium temperature would be ~ -17 o C; For recent climate the equilibrium temperature is ~ +15 o C This is maintained by greenhouse gases in the earth atmosphere, such as water vapor and CO2 Greenhouse Gases

4 Holland, Cherry Creek Science Teachers Nov 2010 (Trenberth etal 2009)

Gases that raise the temperature: – Water Vapor (H 2 0), Carbon Dioxide (CO 2 ), Methane (CH 4 ), Cloroflourocarbons(CFC), Ozone (O 3 ), Nitrous Oxide (NO x ) – Usually combined into CO 2 -equivalent units Gases and droplets that cool the earth: – Sulphates (SO 2 …) Examples of Gases Important to Climate 5 Holland, Cherry Creek Science Teachers Nov 2010

Internal Feedbacks of the Climate System 6 Holland, Cherry Creek Science Teachers Nov 2010 Current Climate Ice Age Runaway Warming Increasing Temperature Tipping Points Generally maintain a “stable” climate, but major excursions can lead to transition to another climatic state (tipping points)

Historical Temperature and CO2 Changes 7 Holland, Cherry Creek Science Teachers Nov 2010 lwf.ncdc.noaa.gov/paleo/globalwarming/images/

Variability: – Variations in solar output and wobbles in the tilt of the earth (range of time scales); – Direct Impacts on the climate system (volcanoes, asteroid impact); – Internal variability); Change – Continental drift (forever) – Ice age variations (millenia) – Solar decline (eons) – Human influence (occurs in decades…lasts for centuries). Why Does the Climate Vary and Change? 8 Holland, Cherry Creek Science Teachers Nov 2010

Volcanic Eruptions 9 Holland, Cherry Creek Science Teachers Nov 2010 Pinatubo

The Year without Summer (1816) 10 Holland, Cherry Creek Science Teachers Nov 2010 After a series of major volcanoes, Mt Tambora (Indonesia) erupted in 1815 to become the largest in recorded history; The resulting solar energy decrease due to the global distribution of dust led to the year without summer (“Eighteen Hundred and Froze to Death!”); More than 71,000 people died of which only ~12,000 were direct; Initiated mass migrations and permanent cultural changes. Wikipedia

Ice Age – Removal of CO 2 – Growth of ice sheet Rapid Warming – Increase of CO 2 – Shrinking of ice sheet Tipping Point Examples 11 Holland, Cherry Creek Science Teachers Nov 2010

Ice-Sheet Tipping Points 12 Holland, Cherry Creek Science Teachers Nov 2010 Most sunlight reflected Most sunlight absorbed

Land-Ice Tipping Points 13 Holland, Cherry Creek Science Teachers Nov 2010 NASA

Methane Tipping Points 14 Holland, Cherry Creek Science Teachers Nov 2010 Permafrost melt releases stored methane, a potent greenhouse gas that decays to CO 2 which initiates more warming and more permafrost melt, and so on.

Impact of Anthropogenic Changes 15 Holland, Cherry Creek Science Teachers Nov 2010 lwf.ncdc.noaa.gov/paleo/globalwarming/images/ Homo Sapiens Evolution 100,000 y 10,000 y 100 y

Internal Feedbacks of the Climate System: Anthropogenic Change Impacts 16 Holland, Cherry Creek Science Teachers Nov 2010 Current Climate Ice Age Runaway Warming Greenhouse Warming Increasing Temperature Tipping Points

Predicting Climate Variability and Change Holland, Cherry Creek Science Teachers Nov 2010 (Meehl et al 2006) (Holland 2008) “Variability” and “change” are hard, indeed often impossible, to logically separate. How do we understand and predict the consequences of change? While history can give us some clues, climate models are the only useful tool. 17

Evolution of Climate Prediction 1960s: Simple Radiative Balance Models 1970s: Pioneering Climate Modeling 1980s: IPCC Fully Established 1990s: Climate Modeling Projections with Skill at Global and Century Scale, Statistical Seasonal Predictions 2005: Wide Acceptance of Global Warming as a Major Issue for Humankind (IPCC Nobel Prize) 2006-Present: Serious Discussion on Impact of Global Warming, and Focus on Decadal Regional Predictions Holland, Cherry Creek Science Teachers Nov

19 Holland, Cherry Creek Science Teachers Nov 2010 Why Decadal Regional Predictions? Vulnerability is Directly Related to: - Predictability of the hazard - Communication of the threat Holland ESSL 0807…Slide 19 Direct Damage>$80 B Indirect Damage >$30BIndirect Damage >$40 B

Why is Model Resolution Important? Holland, Cherry Creek Science Teachers Nov 2010 IPCC Global Grid (180 km) IPCC Decadal Grid (55 km) Current Weather Model Grid (1-2 km, would completely cover the area) 20

We are Now Able to Realistically Simulate High Impact Weather 21 Holland, Cherry Creek Science Teachers Nov 2010 North Atlantic 4 km 2- way nested NRCM Simulation.

Last IPCC Assessment Century Model Grid Spacing ~180 km; Next IPCC Decadal Model Grid Spacing ~55 km. Increased Computing Power Required: ~100 fold Increased Computing Power Required to get to Current Weather Capacity: ~100,000 fold By Moore’s Law of doubling power every 2 years this will take >40 years 22 Holland, Cherry Creek Science Teachers Nov 2010 So What is the Big Deal? Can’t We Just Run the Climate Models at the Required Resolution? 4 Dimensions: 3 Spatial plus Time

Nested Regional Climate Modeling for Multi-decadal Regional Climate 23 Holland, Cherry Creek Science Teachers Nov km 12 km 4 km Global Model: 3 Ensembles from NRCM: , , , 3 ensembles at 36km, 1 at 12 km, specific cases at 4 km. Use of statistical downscaling to fill in intermediate periods Supported by: NSF, DOE, Offshore Oil Industry, Willis Re.

Our Goals in Undertaking Decadal NRCM Predictions 24 Holland, Cherry Creek Science Teachers Nov 2010 To develop experience with high resolution climate forecasting; To provide objective information on: -Variability and changes in high impact weather; -Probabilistic assessment of predictability; and, To work directly with industry, government planners and societal groups to: -Realistically assess their level of vulnerability; -Develop suitable planning, mitigation and adaptation strategies.

Colorado Importance: April Snow Depth 2005 NRCM 12 km (m) 2046 CCSM3 T85 Observations (cm) National Hydrologic Remote Sensing Center 25Western States Water Council 1109

Holland, Cherry Creek Science Teachers Nov 2010 “Climate is what you expect, weather is what you get.” And According to Mark Twain! 26 Tracy Katrina Andrew

Summary Holland, Cherry Creek Science Teachers Nov 2010 Our climate is driven by solar output, but organized by internal processes: Distribution of land and sea, greenhouse and cooling gases, preferred areas of cloudiness and clear; Climate varies considerably: Diurnal, seasonal, biannual, decadal, centurial, millennial: Some is from natural internal processes as the climate “sloshes around inside its boundaries”; Some arises from external forcing such as: solar variations, volcanoes, meteorite impact; Human-released gases are having a substantial impact on our climate: The planet is demonstrably warming; There is the possibility, indeed probable likelihood, that we shall pass a tipping point to runaway change in the next few decades’ We are just starting to understand the full implications for regional climate changes. 27