The expression of environmentalism in politics may have begun in the 1960s through the establishment of activist non-governmental organizations and environmentalist political parties, but issues about climate change and environmental considerations became a prominent global concern in the 1990s - with the Earth Summit in Rio de Janeiro in 1992 and the adoption of Kyoto Protocol in 1997. By the 21st century, sustainability has diffused into the business language and sustainable development has become part of corporate strategies.