How do scientists predict future climate?

Models Scientists use models to predict future climate: including temperature, CO2 levels in the atmosphere, precipitation and more Scientists must create these models using information and science they know Scientists also test or calibrate the models to make sure they are accurate

What is a model? In this case, an equation or lines of programming that has inputs and outputs fortran code from Dennis Shea Very simple climate model T = T 0 + S log 2 (C / C 0 )

Climate Modeling Using computers to do the most impossible math homework known to man

What do we know about CO2? Over the past 425,000 years, cool periods have coincided with times when the CO 2 concentration in the atmosphere was lower. When there is less CO 2 in the atmosphere, the greenhouse effect is reduced and the world cools. The blue and red line indicates the variation in average global temperature compared with the 1961–1990 average. The green line shows the concentration of CO 2 in the atmosphere. (Pay close attention to the right- hand edge of the graph.) This graph shows four eras when the world was cooler than it is today. These are separated by brief warm periods, like the one we are now in.

What do we know? Atmosphere Land & PlantsFossil Fuels Oceans Simplified carbon cycle

Calibrating a model Scientists need to make sure the model works They check the model by comparing the model’s prediction with measured data

Resolution

Graph that includes temperature predictions from 20 different models

Several Models Show the Same Trend obalTemp.cfm

Climate Modeling You be the climate scientist! What might cause carbon emissions to change in the future? (brainstorm)

What does the future hold? What will happen if we keep emitting CO2? 1 gigaton = 1 billion tons ScenarioCO2 Emissions (Gt/year) What this means Current9Same fossil fuel usage High18High economic growth, increased fossil fuel usage Medium11Steady economic growth, slightly increased fossil fuel usage Low4Decreased fossil fuel usage

What is IPCC? Intergovernmental Panel on Climate Change (IPCC) is an international organization that includes scientists and representatives of governments around the world. It reviews the most recent scientific, technical and socio-economic information relevant to climate change HOWEVER It does not conduct any research It provides policy makers (congress or governments) with an objective report of the scientific evidence of climate change, its impacts and possible responses.

How Does it Work? Thousands of scientists from all over the world contribute to the work of the IPCC ▫None of them are paid by the IPCC IPCC aims to reflect a range of views and expertise Review is an essential part of the IPCC process ▫Ensures an objective and complete assessment of current information

nearly 1300 authors 2500 reviews of the report a consensus report (consensus = everyone agrees) report intended to be neutral (for policy), to reflect a broad range of views and perspectives, and to include the most up-to-date scientific information. IPCC Scientific Assessment Report

Oslo, 10 December 2007 The Intergovernmental Panel on Climate Change and Al Gore were awarded of the Nobel Peace Prize "for their efforts to build up and disseminate greater knowledge about man-made climate change, and to lay the foundations for the measures that are needed to counteract such change".

Many Different Scenarios for the Future

Chapter 5 - Emission Scenarios: Figure 5-1 Many different Scenarios for the Future

IPCC predicts… short video of IPCC projections

NEXT TIME… What do models predict for the future climate of Colorado?

Future projections Observed and Projected Temperature Rise for the Southwest The average temperature in the Southwest has already increased roughly 1.5°F compared to a baseline period. By the end of the century, average annual temperature is projected to rise approximately 4°F to 10°F above the historical baseline, averaged over the Southwest region. The brackets on the thermometers represent the likely range of model projections, though lower or higher outcomes are possible.

Future projections Projected Change in Spring Precipitation, Percentage change in March-April-May precipitation for compared to for a lower emissions scenario (left) and a higher emissions scenario (right). Confidence in the projected changes is highest in the hatched areas.

Future Drought Projections (Courtesy Wiley Interdisciplinary Reviews, redrawn by UCAR.