In the face of rising global temperatures, deploying technologies to change Earth's climate has gone from thought experiment to reality. We already capture carbon and store it underground. Now some researchers are suggesting we should spray the clouds with particles to reflect sunlight, fertilize the oceans to promote carbon-absorbing plankton growth, or build a gigantic shade that orbits Earth and opens as needed to shield the planet from the sun. Welcome to the Anthropocene — the era of humans engineering the world in unprecedented ways.

What do we need to know before someone pushes start on a large-scale geoengineering attempt? And what Earth-altering experiment should we try first?

Five leading researchers answered those questions and gave us their take on the risks, as well as the thorny ethical and legal issues that come with unleashing a technology that could span countries, cultures, and generations.

• Janos Pasztor, climate policy expert and executive director, Carnegie Climate Geoengineering Governance Initiative: We aren't ready to engineer the climate
• David Dana, legal scholar, Northwestern University: Talking about geoengineering is distracting
• Jane Long, energy and climate scientist: It's time to investigate geoengineering technologies
• David Keith, climate and energy researcher, Harvard University: Solar geoengineering needs at least another decade of research
• Matthew Watson, geoengineering researcher, University of Bristol: We need to be sure the geoengineering cure isn't worse than the disease