Its time for another series here on the World Around Us, so the next big thing we’re going to spend a few weeks talking about is something that is happening to the world around us. That big thing has the potential to change where a billion of us live, where and how we grow our food, where it rains and where it doesn’t, how ocean currents circulate around the globe, or not, what can even live in the ocean. In short, this phenomenon stands to transform the world beyond the experience of any of us, of any human being that has ever lived. I’m talking of course about climate change, and we’ll spend the next several weeks looking in detail at science behind this multi faceted phenomenon.
Climate change simply refers to a change in the overall
global average temperature and the associated shifts in weather patterns that
accompany the change. The Earth’s climate has changed many, many times over the
course of Earth’s history, generating climates both colder and warmer than what
we experience, on average on Earth today. These shifts typically take thousands
of years. There are various reasons the climate changes, for example the
intensity of the sun has changed over time, the Earth’s orbit and thus distance
from the sun varies, the processes of plate tectonics move the continents
around which changes ocean and atmospheric circulation and thus heat
distribution patterns, the composition of the atmosphere has changed, climate
has even been effect by extra terrestrial objects. For the past 2 million
years, the Earth has experienced, not a steady temperature, but a consistent
pattern of alternating average temperatures, with cooler periods that resulted
in long stretches of glaciation in the northern hemisphere, alternating with
warmer periods, during which time the glaciation receded. We’re in one of those
warmer in between glacial periods now. But instead of cooling back off and
plunging the northern hemisphere back into ice, evidence points to a small increase
in average temperature having occurred already, and puts us on the brink of
larger increases in the near future. We are perhaps leaving this ice age
pattern and moving into a different climate regime.
It should be clear then, that climate change is a normal
occurrence on Earth. What is all the fuss about then? Because, just as we have
loads of evidence about how climate has changed in the past 500 million or more
years, we also have loads of evidence about what the consequences of those
climate changes have been. What we find is that rapid and dramatic climate
change represents an existential crisis for most living organisms. Rapid
changes in climate often accompany mass extinction events, when 60, 70, 80, 90%
of families of organisms disappear from the fossil record. So that dear
listeners, is the thing to be worried about. If you like how things are on this
planet currently, be aware, things are likely to change, not quite on the time
scale of your life, but possibly not too much longer than that. The processes
of evolution have done an amazing job of repopulating the Earth after these
mass extinction events, in fact evolution seems to happen most rapidly when the
physical environment changes. Knowing that, I have no doubt that life on Earth
will go on and even flourish. No, climate change is ultimately an existential
crisis for us. Humans have evolved in a very narrow window of relative climate
stability, and all of what we would call the development of agriculture and
modern civilization has occurred in this briefest of moments in this
interglacial period. As far as we know biologically, its only ever been about
this warm, or colder, in our evolutionary period. Its never been warmer, and
warmer is where it appears we are going, fast. While the Earth has certainly
been there before, we never have, and that reality could have serious
consequences.
Join us in the coming weeks as we attempt to explain the
science of what is happening, how we know what we know, where all this might be
headed and what we can do about it. It’s a topic laden with emotion, political
and economic baggage but I think you will find, the science is fascinating.
From that point of view, we are truly living in interesting times.
