Citibank will lend and invest $100 billion over the next decade in projects that reduce the effects of climate change. This is part of a plan the global bank has developed with the help of a Boston environmental advocacy group, called Ceres. Ceres, founded 25 years ago, enlists a network of institutional investors to convince businesses to follow environmentally sensitive policies and practices. Citibank said it will look for opportunities to finance programs that reduce greenhouse gases, increase access to clean water, and provide low and moderate-income communities with affordable housing. Citi had made a smaller $50 billion commitment in 2007 and was able to lend that money three years ahead of schedule. The $100 billion investment builds on this earlier work, the bank said.