Energy portfolios across the world are rapidly evolving in order to meet the energy demands of a growing population, and to address the challenges posed by the accumulation of greenhouse gases in the atmosphere. Every energy source, renewable or fossil fuel–based, impacts the environment. CIRES scientists study energy production’s “shadow,” that is, the cascading impacts of the new energy economy on air, water, and land resources. Researchers at the Institute also seek scientific understanding of the environment that can help others more successfully implement new energy sources. CIRES researchers study all aspects of the environment, and are thus uniquely positioned to explore important questions about the energy-environment nexus.