The world faces an unprecedented challenge: to change the high-carbon energy DNA of the global economy in the next three decades to low carbon. This requires directed technological change on a historic scale.

It could well fail, and with failure will come a planet wrecked by climate change. At Tuesday’s UN climate summit, nations began the negotiations to last through 2015 that are our last chance to change course.

The reasons we need to change course on the economy, energy and environment are diverse and interconnected. They include persistence of extreme poverty and rising inequality; human-induced climate change; the destruction of biodiversity; and, most generally, the many challenges of a large and growing world economy and population that press far too hard on the earth’s fragile ecosystems and resources.