Planning for the Future with Climate Models

Schematic for Global Atmospheric Model

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by Yun Zheng

Most people are familiar with weather because it affects their daily lives. People use weather forecasts as a statistical tool to help them decide whether or not they should bring an umbrella tomorrow, plan a picnic this coming weekend, or stay at home when a storm is coming.

Weather refers to physical atmospheric phenomena, such as rain, fog, and temperature. Climate differs from weather in that it refers to the long-term average of weather over a region. For example, people in the northeastern U.S. can expect hot summers and cold winters based on the weather patterns over the past few decades. People don’t often think about climate as much as weather because most people don’t often make long-term term decisions, such as starting a business or investing in property, based on the long-term climate or how it might change.

But in today’s world, climate models and forecasts are increasingly important to the public. With changes in the earth’s climate and more frequent extreme weather events for example, more people are concerned with how to adapt to future environments and prepare for the worst. Climate models can help people plan for the long term. These mathematical tools were formulated in the early 20th century and developed to represent the earth’s climate in the past, present, and future. The military spearheaded initial atmospheric measurements and model development during World War II and for pre-Cold War preparations.

According to the National Oceanic and Atmospheric Administration “Climate models are computer-based simulations that use mathematical formulas to re-create the chemical and physical processes that drive Earth’s climate. Climate models are systems of differential equations based on the basic laws of physics, fluid motion, and chemistry. To run a model, scientists divide the planet into a 3-dimensional grid, apply the basic equations, and evaluate the results. Atmospheric models calculate winds, heat transfer, radiation, relative humidity, and surface hydrology within each grid and evaluate interactions with neighboring points.”

Climate models became more prominent in the early 1960s due to growing interest and curiosity with the earth’s climate. But observational data, scientific knowledge, and computer capabilities were still limited. The turning point in climate modeling came more recently with advancements in technology and observational methods. Climate models rely on comparisons with real-world data to verify the accuracy of climate predictions. Because models are able to reproduce past and present climate, there is more confidence in predictions of the earth’s future climate.

Observational methods have been one of the difficult challenges to climate modeling because not everything on earth (e.g. in deep oceans or the upper atmosphere) can be measured. In addition, these measurements are much more difficult to capture over long time periods, due to the lack of sophisticated instruments. Today, with better observational data and advanced computational skills, scientists have been able to improve climate predictions and the understanding of the earth system.

Scientists from Cornell University and several graduate students are actively involved with global climate change modeling and research. Peter Hess, professor of biological and environmental engineering, and Natalie Mahowald, associate professor of earth and atmospheric sciences, are members of a large group of scientists nationwide working on the Community Earth Systems Model (CESM), managed by the National Center for Atmospheric Research, with funding from the National Science Foundation and the U.S. Department of Energy.

CESM is a fully-coupled, community, global climate model that provides state-of-the-art computer simulations of the Earth’s past, present, and future climate states. The model and its output is part of a vast online archive hosted by the U.S. Department of Energy for all scientists to review and use, and the results of that work provide part of the basis of the scientific recommendations of the United Nations Intergovernmental Panel on Climate Change (IPCC).

Government leaders and policymakers from around the world have relied on the scientific assessment reports issued by the IPCC to as the basis for negotiations on global action to address climate change under the UN framework convention on climate change (UNFCCC) and Kyoto Protocol. The fifth IPCC assessment report is set for release in 2014. To find out more information about climate change and climate models, see: http://www.ipcc.ch/

Climate change skeptics often argue that climate models are inconsistent and incomplete, and that the inaccuracy of weather forecasts is analogous to the unreliability of all weather and climate predictions. They often focus on the many drawbacks of the models, highlighting the uncertainties and putting emphasis on what the models cannot do rather than what they can do.

However, biologists and doctors often utilize models that are may be incomplete, but are still useful tools in helping them diagnose diseases. Economists use quantitative models to provide simplified analyses of complex processes in our economy across different sectors, such as the insurance industry and the stock market. No model is perfect, but all models are worthwhile tools that can help with decision-making.

Many officials are interested in utilizing advanced climate models to help them better prepare for climate change. After Hurricane Sandy swept the eastern coast of the U.S. in 2012, local officials became much more keenly aware of the need for better, localized climate change data from models to help them prepare for extreme weather events in order to abate high damage and death rates. City engineers and architects are building and designing infrastructure with future climate change in mind to increase resiliency, especially to hurricane-related damages such as storm surges. By using climate predictions to extract information about the future climate, people can better prepare cities and communities for the climate they will live in.

While a climate model cannot provide exact details on everything about the future climate, it does provide researchers and policy makers with information on general trends that can be expected in the future. The earth system is complex to model, but significant improvements have been made possible by human advancements and a growing interest in climate change science.

According to Tracy Sun, a graduate student at Cornell University, “The pursuit of the knowledge about the world never stops, and something we believed in previously might turn out to be wrong after decades, so there is no need to question the lack of knowledge.” The new era has come for people to shift the focus to the usefulness of climate models, rather than focusing on their shortcomings and uncertainties, in order to make better decisions based on scientific information.

Yun Zheng

Yun Zheng

Yun Zheng earned her B.S. in Earth and Environmental Engineering from Columbia University’s Fu Foundation School of Engineering and Applied Science in 2010. She worked with her advisor, Natalie Mahowald, at Cornell University on the National Center for Atmospheric Research’s Community Earth System Model (CESM). She has recently graduated from Cornell University with her M.S. degree in Civil and Environmental Engineering. Her thesis is titled “The Future of the Amazon Post 2005 and 2010 Droughts: An inter-Comparative Model Study”.



Category: Climate Change Forum

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