# Presentation: 925625

## Near-term Climate Change Scenarios for Central America

**Obtained from a Regional Climate Model**

- Presented by: Bob Oglesby
- NASA/MSFC

- The Climate Change Team: Bob Oglesby, Jayanthi Srikishen, and Dan Irwin from
- NASA/MSFC and Jose Hernandez and David Erickson from DOE/ORNL
- With assistance in model evaluation from Jasna Pittman and Bob Atkinson of the
- NSSTC Climate Group

## The key task is to evaluate the relative roles on climate change 

- for Central America of effects such as global warming due to
- greenhouse gas emissions and continuing land use changes.
- This presentation focuses on greenhouse gas induced climate
- change, i.e., ‘global warming’ and its impacts on Central
- American climate over the next 20 years.
- On Thursday, I will talk about the work needed to evaluate the
- impacts of land use changes on Central America climate.

**PROJECT OBJECTIVES**

## The Intergovernmental Panel on Climate Change (IPCC) 

- (http://www.ipcc.ch) has devised a series of global climate model
- runs starting over the period of the 20th century (for which
- observations exist) and then projecting scenarios of greenhouse gas
- emissions through the 21st century.
- These runs have been repeated  several times over the past two
- decades as modeling capabilities have improved.
- The most recent ensemble IPPC runs were completed in late 2004

## Slide 4

## The IPCC scenarios can be categorized into two groups: a set 

- of ‘commitment scenarios’ and a number of ‘science scenarios’
- that explore alternative future emissions outcomes.
- The IPCC SRES science scenarios that were recommended to
- the global coupled climate modeling groups include A2, A1B
- and B1.
- The A2 (business as usual-BAU), A1B (weak stabilization) and
- B1 (strong stabilization) scenarios consist of five-member
- ensembles run for the period 2000-2100.

## BAU assumes no change from current rapid increases in 

- greenhouse gases
- The stabilization scenarios assume that mitigating actions will
- lead to stabilization at a high level of greenhouse gases (weak
- stabilization) or a much lower level (strong stabilization).
- Commitment scenarios are then run with the concentrations of all
- atmospheric constituents in A1B and B1 held constant at year 2100
- values, and the model continues to the year 2200 with five-member
- ensembles.
- There is also a 20th century commitment scenario that freezes
- concentrations at year 2000 levels, and the model is run to the
- year 2100.

## The NCAR CCSM3.0

- *CCSM3.0 is the most recent release of the global coupled
- climate model produced by the CCSM community
- *Contains new model physics and supports new model
- resolutions.
- *IPCC runs made at T85 resolution (about 140 km in latitude
- and longitude.
- *Output for our run is stored on the archival system at Oak
- Ridge National Laboratory
- *(Permission from the makers of the run is required to use
- This output for any other purpose.)

## Slide 8

## The MM5 Model System

- sigma-coordinate model designed to simulate or predict mesoscale and regional-scale atmospheric
- circulation.
- It has been developed at Penn State and NCAR as a community mesoscale model and is continuously
- being improved by contributions from users at several universities and government laboratories.
- The Fifth-Generation NCAR / Penn State Mesoscale Model (MM5) is the latest in a series that
- developed from a mesoscale model used by Anthes at Penn State in the early 1970’s.
- Since that time, it has undergone many changes designed to broaden its usage. These include (i) a
- multiple-nest capability, (ii) nonhydrostatic dynamics, which allows the model to be used at a
- few kilometer scale, (iii) multitasking capability on shared- and distributed-memory machines,
- (iv) a four-dimensional data-assimilation capability, and (v) more physics options.

**The MM5 Model System**

## Regional Model Climate Change Runs

- *Used BAU Scenario, so as to maximize possible effects due to
- greenhouse gas-induced warming
- *Global Climate Model run (from the NCAR CCSM3) provided
- output 4X daily; this serves as the large-scale forcing for the
- MM5 Regional Climate Model
- *Four years were chosen in conjunction with Central American
- partners: 2005; 2010; 2015; and 2025
- *2005 serves as a ‘present-day control’ the remaining years project
- possible short-term climate changes over the next 20 years

## Regional Model Climate Change Runs, Cont.

- *For these runs, we increased the model resolution to 36 km for the
- outer domain and 12 km for the inner domain.
- *The inner domain (which includes all of Mesoamerica and adjacent
- oceans is the one from which we obtain our main results (such as will
- be shown later)
- *The outer domain serves two purposes: 1) It steps the forcing down
- from the scale of the global model (approximately 140 km) to the
- fine resolution of the inner domain; 2) It allows for analysis of
- large-scale effects and forcings influencing Mesoamerican climate.
- *At this fairly high resolution and large domain, it takes almost two
- days of wall-clock time to run a single model month on one of the
- world’s fastest supercomputers at Oak Ridge National Laboratory!

## Slide 12

## As of this workshop, the wet season months of June, July, and August,

- have been completed for the four years 2005; 2010; 2015; and 2025.
- The years 2005, 2010 and 2025 have been completed for September.
- The dry season months of January and February are currently
- underway.
- Once the dry season runs are finished, the remaining months will
- be made, if time and resources allow.
- (The runs have taken more computer resources than originally
- anticipated; we had hoped to have all months complete by this
- workshop. But in the modeling game, one never knows how it
- will go until the runs are actually underway!)

## The next slides show some of the basic model results.

- First, we compare MM5-simulated precipitation and soil moisture
- with observations.
- For precipitation, we use the TRMM v6 surface rain rate product (a
- radar-reflectivity based dataset) at 0.5 deg resolution (approximately
- 50 km)
- For soil moisture, we use 10.65 GHz reflectivity from the AMSER-E instrument on the Aqua satellite at 25 km resolution.
- It is important to realize that we are comparing only one model year
- to one year of observations. Still, the comparison is striking!

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## Observed soil moisture for 17 June 2005 from the ......... instrument

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## Next we show potential future changes as simulated by the

- model. We focus on surface temperature and precipitation.
- Emphasis is on the differences between 2025 and 2005 (i.e., the
- largest change in greenhouse gases).
- While some strong signals are seen, it is also clear that model
- variability plays a large role.
- To help bring this out, we also show some differences between
- 2015 and 2005.

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## Overall, the tendency is for warmer and wetter conditions over

- the next 20 years.
- BUT there are significant regional differences.
- And interannual variability clearly plays a major role. We have
- limited capability to do multi-year MM5 runs, but we are actively
- investigating interannual variability in the global CCSM3 model.
- More results, analysis, and interpretations will be placed on the
- Website as we obtain them.