Climate change is about big things: melting ice sheets, rising seas, the feverish temperature of the planet. But scientists say it’s also about little things — namely, microbes. Like all life forms, microbes will feel the impacts of climate change. The way they respond could have huge implications for the rest of us. For instance, microbes will help determine whether natural sources of greenhouse gases rise or fall in a warming world. And they are key to ecological resilience in the face of environmental stress. That’s why a group of scientists issued a consensus statement calling for more research on the topic in this week’s issue of Nature Reviews Microbiology. Ominously, they called it ”Scientists’ Warning to Humanity.” The Times spoke with Victoria Orphan, a microbial ecologist at Caltech who helped write the statement, about why we shouldn’t overlook microbes.