Is climate change a serious threat to human health? Simple logic would suggest the answer is yes, a point that the Obama administration is using to build support for the president’s effort to make climate change a centerpiece of his final months in office. A White House report listed deepening risks. Asthma will worsen, heat-related deaths will rise, and the number and traveling range of insects carrying diseases once confined to the tropics will increase. But the bullet points convey a certainty that many scientists say does not yet exist. Scientists agree that evidence is growing that warmer weather is having an effect on health, but they say it is only one part of an immensely complex set of forces that are influencing health.