Climate change has been in the headlines for years. I tell my undergraduate students that the U.S. has been discussing climate change for their entire lives. It was 1992 when countries around the world came together in Rio de Janeiro and committed to preventing dangerous climate change. At that time, the U.S. ratified an international agreement that Americans, together with other rich countries, would take the lead in greenhouse gas emission reduction, but so far, we've done little to follow through on that commitment. The climate change issue lingers. Uncertainty about what to do and when to do it seems to plague our politics and our dinnertime conversations. Many of us have simply put our head in the sand. It would just be a lot easier if we could pretend that it isn't true.
That might be about to change. This week we expect a major statement, an encyclical, from Pope Francis about environmental protection and its significance to the Church, and we expect climate change to feature prominently in it.
I am not a theologian and can't comment on the religious dimensions of what Pope Francis is likely to say, but I have been studying climate change for decades. As a scientist I know that it is time to heed the Pope's words and embrace his call to action.
There are many reasons why the Pope is concerned about climate change, and why you should care about it too. The science is not as controversial as you may have heard. Well-funded campaigns have been effective in confusing the public about climate change and science itself is poorly equipped to explain its findings to the public. Nothing in science is ever completely certain, but what we know about climate and human-caused climate change is about as certain as science gets. Atmospheric chemists understand well that carbon dioxide and the other greenhouse gases increase global average temperature, and climate observations, coupled with climatological models, tell us that the that the beginning effects of climate change are already happening around the world.
That's not to say that there isn't plenty of debate in climate science -- there is, and the debate is important because we are still learning about the local consequences of climate change, about where the greatest risks to climate change lie, and about crucial developments in the climate system that may intensify or soften the impact of greenhouse gases.
We have much to discover yet, but the science debate is simply not as uncertain as many newspapers, and many politicians, would have you believe. Many species and ecosystems will decline from climate change. Patterns of plants and animals around the globe are determined mainly by two forces: the effect of history, and the effect of climate. Species adapt to particular climates, whether they be hot and dry desert plants or salt and cold-tolerant marine fish. This means that when the climate changes, nearly everything on Earth is affected. Plants and animals will track the change in climate if they can, and if they cannot, they will decline and may even become extinct. We worry about some life forms that well reflect and take advantage of change: pests and disease, for example. We also worry that other species that filter our water, and provide us life-giving service as well as with our cultural heritage may decline. If only 10 percent of species now alive cannot adjust to climate change and go extinct (a conservative estimate of possible extinction, by the way) we would lose as many of 1,000,000 of our fellow earthlings. Climate change is not just about saving nature; it also is about saving people.
While humans inhabit almost the entire globe, we still live at the mercy of the climate. It brings the water -- not too little not to much -- that makes agriculture possible. It also brings natural disasters that threaten lives and livelihoods. The Notre Dame Global Adaptation Index, for example, reminds us that the greatest vulnerability to climate change is in the least developed parts of the world, places where public health, agricultural practices, access to clean water, and other basic capacities related to climate are limited. The Index shows that it would take more than 100 years for poorer countries to be as ready for climate change as developed countries are already. We cannot wait 100 years; the effects of climate change are appearing now, and will be even more conspicuous in the coming decades. We need rapid investment to resist the effects of climate change in hundreds of countries around the world. And while ahead of the developing world, hurricane Sandy and the California drought show that wealthy countries like the U.S. have much adaptation to do too.
Climate models suggest that we are dangerously close to a global tipping point, a level of greenhouse concentration in the atmosphere that will produce catastrophic amounts of climate change, but our fate is not sealed. We can do something about it.
Many of the technologies that we could effectively use to solve the climate crisis are already available. They just need the right political stimuli, the right economic incentives, to be put into place. Consumers need access to climate-smart energy alternatives. Economies that can provide such alternatives and develop clean, sustainable energy production are more likely to the lead the world in economic growth. The same goes for adapting to climate change: better incentives and understanding of climate change risk can drive investment that can both save lives and promote sustainable economic development. We are running out of time, but hope is not yet lost.
These are things that Pope Francis knows, and you should know them, too. With knowledge comes responsibility for action, a responsibility that the Pope will certainly insist that Catholics, and all human beings, must take up. We should listen carefully to what he has to say.