The William and Flora Hewlett Foundation makes grants to solve social and environmental problems in the USA and internationally. The Foundation’s grant making for its environmental sub-program in Climate and Energy makes grants to strengthen global climate policy. The Foundation also funds improvements in transportation to reduce air pollution — focusing on China, India, Europe, and the United States. Most of Hewlett’s grants are by invitation. However, the Foundation accepts letters of inquiry (LOIs) in certain programs — including Climate and Energy. LOIs can be submitted at any time. Link