Last month, during a trip to Europe, I mentioned that I plan to invest $1 billion in clean energy technology over the next five years. This will be a fairly big increase over the investments I am already making, and I am doing it because I believe that the next half-decade will bring many breakthroughs that will help solve climate change. As I argued in this 2010 TED talk, we need to be able to power all sectors of the economy with sources that do not emit any carbon dioxide.

But when it comes to preventing the worst effects of climate change, the investments I make will matter much less than the choices that governments make. In Europe I got to talk about these choices with several political leaders, and in this post I want to share the steps that I encouraged them to take.

I think this issue is especially important because, of all the people who will be affected by climate change, those in poor countries will suffer the most. Higher temperatures and less-predictable weather would hurt poor farmers, most of whom live on the edge and can be devastated by a single bad crop. Food supplies could decline. Hunger and malnutrition could rise. It would be a terrible injustice to let climate change undo any of the past half-century’s progress against poverty and disease—and doubly unfair because the people who will be hurt the most are the ones doing the least to cause the problem.

In addition to mitigating climate change, affordable clean energy will help fight poverty. Although the Gates Foundation does not fund energy research (my investments are separate), we see through our work with the poorest how the high price of energy affects them by adding to the cost of transportation, electricity, fertilizer, and many other things they need.

I do see some encouraging progress on climate and energy. Environmental advocates deserve credit for getting climate change so high on the world’s agenda. Many countries are committing to put policies in place that reflect the impact of greenhouse gases. The cost of solar photovoltaic cells has dropped by nearly a factor of ten over the past decade, and batteries that store energy created by intermittent sources like solar and wind are getting more powerful and less expensive. Since 2007 the United States has reduced its greenhouse gas emissions nearly 10 percent. Since 1990 Germany has reduced its energy-sector emissions by more than 20 percent.

World leaders will take another critical step this December at a major meeting in Paris called COP21, where they will discuss plans to reduce global CO 2 emissions significantly. COP21 can build a strong foundation for solving the climate crisis—but we will need to go even further.

Scientists generally agree that preventing the worst effects of climate change requires limiting the temperature increase to 2 degrees Celsius, and that doing so requires the biggest emitters to cut emissions 80 percent by 2050 and all countries to essentially eliminate them by the end of the century. Unfortunately, while we can make progress with today’s tools, they cannot get us to an 80 percent reduction, much less 100 percent. To work at scale, current wind and solar technologies need backup energy sources—which means fossil fuels—for windless days, long periods of cloudy weather, and nighttime. They also require much more space; for example, to provide as much power as a coal-fired plant, a wind farm needs more than 10 times as much land.

These are solvable problems. If we create the right environment for innovation, we can accelerate the pace of progress, develop and deploy new solutions, and eventually provide everyone with reliable, affordable energy that is carbon free. We can avoid the worst climate-change scenarios while also lifting people out of poverty, growing food more efficiently, and saving lives by reducing pollution.

To create this future we need to take several steps: