Throughout Earth's history the global climate has swung back and forth between warm and cold stages, often with a predictable regularity. During the last million years cold stages known as glacials – ice ages – were long lasting periods punctuated by much shorter warm inter-glacials, like today. Now with more than 10,000 years since the end of the last ice age we should soon be due another. But recent research shows that due to the current global warming a new ice age is unlikely to happen for at least 100,000 years, meaning we are dramatically changing Earth's natural climate cycle.
An ice age is a long lasting period – about 100,000 years – where the global temperature drops by up to 5°C. The cooling is more at higher latitudes where continental ice sheets gradually formed over northern Europe, extending as far south as Germany and across the islands of Ireland and the United Kingdom. They formed because at such low temperatures rain falls as snow, accumulating over time as ice.
Ice sheets also covered a large part of North America and at their maximum were enormous, 3-4km in height. So at that time it was impossible for humans to live in these regions. Today ice sheets, or ice caps, still exist over Greenland and Antartica, where it remains cold enough for snow to build up as ice. But because our global climate is warming fast we can expect a gradual melting of these ice caps over the coming centuries, meaning no ice age.
Changing climates are important because we know that the development and migration of human populations has historically been determined by the weather. Over the past 50,000 years – during the ice age and the warming which ended it – neanderthal and human populations shifted gradually across Europe and Asia. They were displaced largely in response to climate changes. This is illustrated by a new article published in the journal Nature. The study details how genes found in an individual in northwestern Europe 35,000 years ago later reappear in south west Europe at the height of the ice age, 19,000 years ago. This tells us that, as the severity and extent of the ice age developed, populations and their descendants gradually moved southwards, to warmer environments more suitable for human life.
Later, during a warming period 14,000 years ago, the study describes how “another genetic component related to present-day Near Easterners became widespread in Europe”, meaning that at that time the warm climate provided hospitable conditions for the proliferation of these near-eastern people and their descendants across Europe. The point is this: human migration during the last ice age was largely controlled by the climate, and we can expect this to be the case again in the future.
Over time those European people formed settlements in villages, towns, and cities. And during the past few hundred years they discovered how to use coal and oil, carbon based fuels which had over millions of years harnessed energy from the sun (the original source of energy on Earth). The consumption of these fuels unleashed large amounts of carbon dioxide into the planet's atmosphere, so that now, in the 21st century, the Earth experiences an enhanced greenhouse effect, ensuring a world-wide warming. So much so that now it looks like the natural rhythm of the Earth is changing its beat.
Another article in Nature, published in January this year has shown that the current injection of massive amounts of carbon dioxide into the atmosphere should postpone the next ice age by at least 100,000 years. "We are now in a period when our northern summer is furthest from the Sun. Under normal circumstances, the interglacial would be terminated, and a new ice age would start” said lead author Andrey Ganopolski in an interview with the BBC. What he means is that our current warm period (interglacial) should be coming to an end. But because the atmospheric carbon dioxide concentration is so high – and increasing – there is a strong greenhouse effect, meaning we are pushing the onset of the next ice age further and further into the future. Great news one might think. Unfortunately the approaching warm world does not look so good either.
The current warming of the Earth, just like during the end of the last ice age, will result in large-scale migrations of people. Now with a global population of over 7 billion we can expect large human migrations across the planet, as people escape new-world environmental, political and social issues. Flooding, drought, heatwaves, fire, crop failure, and islands sinking due to rising sea levels are already becoming more widespread. The effects will vary regionally, and some locations may even benefit from change. But those are the regions where people will want to relocate, and where host nations will experience the political turmoil associated with such change. There are suggestions that the current exodus from Syria is in part caused by the changing climate in that region.
Humans have taken control over our planet in an accidental fashion – without foresight – and are ultimately leading ourselves on a highly uncertain path. The complete alteration of the natural cycle in and out of ice ages will reshape the future evolution of humans and other species, with unpredictable consequences for life on Earth. "The important thing is that it is an illustration that we have a geological power now. We can change the natural sequence of events for tens of thousands of years", Andrey Ganopolski told the BBC.
How remarkable it is that biology arising on a planet could consciously change the nature of the planet itself, and ultimately its destiny. Think about it: millions of biological organisms actively filling their planetary atmosphere with a gas that is going to destroy them. The act works against the process of evolution itself, where natural selection ordinarily directs organisms not only to reproduce, but also to protect
Not by any stretch of the imagination is enough being done to tackle the greatest crisis of our time. Nature speaks. We do not listen.