Sending dozens of emails a day, making a quick call on WhatsApp, uploading some photos to the cloud, watching a short viral clip on YouTube: it’s all part of the digital daily life around the world. For the individual, it may be “just one photo” or “just a few minutes of video,” but taken together, our collective internet traffic contributes enormously to climate change. Everything a computer, tablet or smartphone does requires electricity. And to generate that electricity, the world still predominantly uses fossil fuels — which produce carbon dioxide and contribute to heat-trapping greenhouse gases. Digital technologies have even...