Natural climate change is real and very natural – without it the earth would be very different to the diverse, complex and dynamic wonder that it is and, more than likely, we would not be here to chronicle it all.
Why? Because climate change is an important driver of evolution; a disturbance factor that jolts so hard that great extinction events happen knocking out whole lineages of organisms and clearing the slate for new diversity to emerge.
Certainly evolution occurs without climate change. There are random errors in the replication of DNA (mutations), genetic drift and the ecological mechanisms that drive allopatric speciation; but the big opportunities emerge when climate change shocks the species compliment out of these slower, more cozy options.
Not everyone believes in evolution and for a long time not many believed in climate change either.
The prevailing wisdom for centuries was that a benevolent God not only created the earth but also kept a gentle and stable hand on the climate. Not surprisingly in the 1830’s when the Swiss naturalist Louis Agassiz claimed after close examination of Alpine glaciers that there were ice ages in the past, he was like a prophet in his own land. Nobody believed him.
Eventually the notion of large changes in climate sufficient to send glaciers careering down alpine valleys did catch on among scientists and soon there were several ideas as to why such changes occurred.
The three that have persisted thanks to garnered evidence are
Solar activity – over the past 10,000 years when sunspot activity is low then the climate cooled into the so-called ‘Little Ice Ages’ and when sunspot activity is high there are warmer periods.
Note that around 1975 global temperatures started rising while solar activity stayed level – some scientists suggest this is evidence for another cause in the latest warming trend.
Milankovitch cycles – the name given to long term (120,000 year) changes in the earth’s orbit that initiate a warming of the oceans that melts ice sheets and releases extra CO2 to the atmosphere that adds more warming due to the greenhouse effect and results in warmer period (interglacials).
Volcanoes – eruptions that release sulfates to the atmosphere have a cooling effect for several years as these compounds reflect incoming sunlight. Volcanoes also release CO2.
These three main causes of natural climate change appear not to have been operating in the latest warming event.
There is scientific evidence that
Rather than too quickly into the anthropogenic climate change issue, imagine for a moment that instead of steam and the internal combustion engine humans had invented fusion power way back in the early 1800s.
So instead of a fossil fuel based economy we generated copious energy with water as a byproduct instead of CO2, would we witness climate change?
Well, yes we would, because natural climate change is real. Although likelihood is that it would be slow and therefore difficult to detect.
Climate change need not be abrupt climate change from our perspective to impact on the process of evolution, only fast enough to affect the rates of reproduction and survival across generations of long-lived organisms, especially the structural ones like trees.
Evidence for a change in something, climate in this case, is not enough. It will not tell us all we need to know to understand the consequences.