Scientists theorize that if global temperatures do rise, the greatest warming is likely to occur

Introduction

Scientists warn that a warming planet threatens human health. A United Nations agency estimates climate change will cause 250,000 additional deaths annually between 2030 and 2050. The threat is multifaceted. Prolonged droughts are causing malnutrition in Africa, while extreme heat is leading to spikes in heat stroke in places as diverse as Baltimore and Paris. Across the globe, changing climes are worsening allergies and increasing the deadly reach of illnesses such as malaria, dengue fever and West Nile virus. But consensus is lacking about what to do. Some experts argue the threat is exaggerated because people will adapt to the changing climate. Others say nations must quickly reduce carbon emissions to limit global warming and protect human health. Environmental activists are amplifying that message. One survey found that respondents ranked climate change as the top threat in 13 of 26 countries polled. In the United States, however, only 27 percent of Republicans — versus 83 percent of Democrats — view climate change as a major threat.