Climate Models: Everything You Ever Wanted to Know, Ask, and Teach Randy Russell and Lisa Gardiner Spark – science education at NCAR All materials from this workshop (including movies) are available online at: spark.ucar.edu/workshops NSTA National - Boston, April 2014

National Center for Atmospheric Research in Boulder, Colorado

Workshop Overview Climate model components Resolution activity Systems Game The Very, Very Simple Climate Model Climate/Carbon Bathtub

Using Models in Education “Essentially, all models are wrong, but some models are useful.” - George E. P. Box (1951)

Evolution of Climate Models Credit: Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4): Working Group 1: Chapter 1, page 99, Fig. 1.2

Climate Model Components Credit: UCAR (Paul Grabhorn)

Resolution: What Does It Mean?

Improving Resolution of Climate Models Credit: Warren Washington, NCAR Grid Cell Sizes 1990s (T42) 200 x 300 km 120 x 180 miles 2000s (T85) 100 x 150 km 60 x 90 miles

Improving Resolution of Climate Models Credit: Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4): Working Group 1: Chapter 1, page 113, Fig. 1.4

Vertical Resolution of Climate Models Vertical Layers 1990s 10 layer atmosphere 1 layer “slab” ocean 2000s 30 layer atmosphere 30 layer ocean Credit: UCAR

Horizontal and Vertical Grid

Hexagonal Grid and Sub-grids Credit: UCAR (Lisa Gardiner)

Resolution: Spatial & Temporal (Time) Timesteps can be a few minutes to 12 hours or more Durations can be hours to centuries

40 km resolution in 1-D model

20 km resolution in 1-D model

10 km resolution in 1-D model

40 km resolution in 2-D model

20 km resolution in 2-D model

10 km resolution in 2-D model

Resolution and Computing Power Double resolution – increase number of nodes – more calculations! One Dimension Two Dimensions 2 times as many nodes 4 times as many nodes

Resolution and Computing Power What if we increase model to three dimensions (space) plus time?

Resolution and Computing Power What if we increase model to three dimensions (space) plus time? 16 times as many nodes – 16x computing power required! This is why we need supercomputers!

Weather vs Climate Models Why do we think we can make meaningful 100 year climate projections when we can’t forecast the day-to-day weather a month from now?

Weather Model vs Climate Model Compare and Contrast Differences (and similarities) between Weather vs. Climate Models Area Covered (scale) Resolution – distance (spatial) and time (temporal) Timespan covered by model runs Impacts on computing resources needed, time required to run models

Weather Model vs Climate Model Area Covered Weather Model – up to about continental size scale Climate Model – global size scale Larger area requires either more computing power/time or lower resolution (spatial and/or temporal)

Weather Model vs Climate Model Resolution and Precision Weather Model resolution typically about 3-10 km timesteps of hourly to 6 hours, forecast for next 3-4 days Climate Models resolutions from about km up to 100 (or a couple hundred) km running computer models can take days or weeks, which would be impractical for weather models Precision – why Wx forecast for Christmas is suspect, but temperature next July is reliable (relationship to chaos)

Weather Model vs Climate Model Timeframe Weather Forecast – hours to days (up to about 10 days) Climate Projection – decades to centuries or longer (climate is usually defined as at least 30 years of observations)

Source: Meehl et al NCAR

spark.ucar.edu/sites/default/files/SystemInMotionMaster.pdf

Greenhouse Effect Review  CO 2 absorbs heat in the atmosphere  When heat accumulates in the Earth system, the average global temperature rises

Increased CO 2 & the Greenhouse Effect  When the amount of carbon dioxide in the atmosphere increases, average global temperature rises.  Longwave radiation emitted by CO 2 is absorbed by the surface, so average global temperature rises

Emissions -> More CO2 in Air -> Higher Temperature 15° 18°

Climate Sensitivity - definition Whenever the amount of carbon dioxide in the atmosphere doubles, average global temperature rises by 3 degrees Celsius. 15° 18° 15° 18°

Learning from the Past (ice cores) Ice age

CO 2 Emissions – Where are we now? In 2014, CO 2 emissions are around 10 gigatons (GtC) per year (10,000 million tons in units used on this graph)

CO 2 in Atmosphere – Where are we now? ice age 396 ppm in 2013  For hundreds of thousands of years, CO 2 varied between 180 and 280 parts per million, beating in time with ice ages  Since the Industrial Revolution, CO 2 has risen very rapidly to about 400 ppm today

Math of Climate Sensitivity When the CO2 concentration in the atmosphere doubles, temperature rises by 3°Celsius (about 5.4°F) Examples:  If CO 2 rises from 200 ppmv to 400 ppmv, temperature rises 3°C  If CO 2 rises from 400 ppmv to 800 ppmv, temperature rises 3°C  Note: as CO 2 rises from 200 to 800 ppmv (800 = 4 x 200), temperature rises 6°C ( = 2 x 3 degrees, not 4 x 3 degrees)

Climate Sensitivity Calculator demo spark.ucar.edu/climate-sensitivity-calculator

Climate Sensitivity Calculator Activity Use the calculator (previous slide) to determine the expected temperature for the various CO 2 concentrations listed in column 1 of the table above (students fill in column 2); then have them graph.

Advanced Climate Sensitivity Math T = T 0 + S log 2 (C / C 0 ) T : new/current temperature T 0 : reference temperature (e.g degrees C in 1820) S : climate Sensitivity (3 degrees C) C : new/current atmospheric CO 2 concentration C 0 : reference atmospheric CO 2 concentration (e.g. 280 ppmv in 1820) Example: What is new temperature if CO2 rises to 400 ppmv (from 280 ppmv)? T = T 0 + S log 2 (C / C 0 ) = log 2 (400/280) = log = = 15.2 degrees C

Dry air mass of atmosphere = x kg = 5,135,000 Gigatons CO 2 currently about 599 ppm by mass (395 ppmv) = % CO 2 current mass = % x 5,135,000 Gt = 3,076 Gt CO 2 current emissions = 9.5 GtC/year Atmospheric fraction = 45% M = M 0 + [0.45 x (3.67 x m)] = 3,076 GtCO 2 + [0.45 x (3.67 x 9.5 GtC/yr)] = 3, GtCO 2 = 3,092 GtCO 2 CO 2 concentration = 3,092/5,135,000 = 602 ppm by mass CO 2 concentration = (602/599) x 395 ppmv = 397 ppmv Math of CO 2 Emissions and Atmospheric Concentration ( ) / 12 = 44/12 = 3.67 GtC vs GtCO 2

Poll: Rising Emissions B A C ? ? ?

B A C ? ? ?

B A C ? ? ? Poll: Emissions rise then steady

B A C ? ? ? Poll: Emissions rise then fall

Very Simple Climate Model demo spark.ucar.edu/simple-climate-model

Why does temperature continue to rise as emission rate declines? Atmosphere CO 2 in Atmosphere CO 2 Emissions CO 2 Removal by Oceans & Plants spark.ucar.edu/climate-bathtub-model-animations-flow-rate-rises-falls spark.ucar.edu/imagecontent/carbon-cycle-diagram-doe

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ALL Workshop Materials are Available Online at: spark.ucar.edu/workshops