High tide in Kiribati, an island nation seen as especially vulnerable to the effects of climate change, like rising sea levels. WASHINGTON — A sweeping new study on the effects of climate change — which the report says is already disrupting the lives and livelihoods of the poorest people across the planet — creates a diplomatic challenge for President Obama, who hopes to make action on both climate change and economic inequality hallmarks of his legacy. The report, published this week by the United Nations Intergovernmental Panel on Climate Change, concludes that the world’s poorest people will suffer the most as temperatures rise, with many of them already contending with food and water shortages, higher rates of disease and premature death, and the violent conflicts that result from those problems. Countries like Bangladesh and several in sub-Saharan Africa that are the most vulnerable to the effects of climate change […]