US Climate and Health Alliance

The health impacts of climate change


Can we at last accept that the climate is changing, that we are making it happen, and that there are profound implications for us? Chris Rapley answers the key questionsNo science is ever completely settled. However, among the tens of thousands of scientists working in the field of climate science worldwide there is almost complete agreement that our climate system is changing, and that human activities are the predominant driving force. This agreement is remarkable given what a belligerent, argumentative lot scientists are, and that they take great pleasure in proving each other wrong. I want to address the following five questions: Has the climate changed before? Are the current circumstances unusual? Is the planet warming (and how do we know)? Is it us (and how do we know)? And does it matter?Yes, on many timescales and for many reasons, not least because the energy output of the Sun varies. As the primary energy source of the Earth system, the Sun drives the motions of the ocean and the atmosphere, as well as energising the photosynthesis on which the food chain of life depends. The Sun’s luminosity has increased by about 30% over the 4.5 billion year lifetime of the planet, and its energy output fluctuates, albeit at the 0.1% level. So yes, the Sun changes, and in doing so it drives changes in the Earth’s climate system.In addition, the growth of the biosphere itself has completely altered the chemistry of the atmosphere. Before the rise of the cyanobacteria, some 2.5 billion years ago, there was no oxygen in the atmosphere. As Jim Lovelock pointed out in his Gaia theory,1 the Earth’s biology isn’t a passenger. It is an active, interconnected part of the system that drives change that affects the climate system. This is especially …

Resource Type
Peer-reviewed article
Chris Rapley
Resource URL
Journal Abbr.
March 19, 2012
0959-8138, 1468-5833
© BMJ Publishing Group Ltd 2012
Climate science

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