To recap, Space-Time is created by a Big Bang nearly 14 billion years ago (BYA). It expands faster than the speed of light, and as it does so the plasma energy cools down and the first atom is formed: hydrogen.
Clumps of hydrogen become solar systems; ours has 4 rocky plants and four gas giants formed from an earlier star’s dying explosion, a supernova, some 5 BYA. In its life, and even more its death, a star creates the progressively larger elements, including Nitrogen, Carbon, Oxygen and Phosphorous. These are the key elements of organic life. And, of course, hydrogen. Both as water and as a central player in molecular machinery or chemistry of life.
It takes about a billion years or the first evidence of life from these elements combining into molecules. Earth is not the gentle planet she is now, but a fierce rock that is only slowly developing an atmosphere. Earth is constantly changing over geological time, including periods when the entire planet was entirely covered by ice: Snowball Earth.
From the first atoms that create a molecule that is able to make a copy of itself, this molecular life becomes more complex leading to cells. Sex, the sharing of genetic matter, is a relatively recent discovery for these cells, but once initiated accelerates cells progress in complexity leading to multi-cellular organisms.
For our line the fish are the first to develop a backbone, a group called vertebrates, meaning to have vertebra – the bones that protect our spinal cord and carry our torso and head.
From fish to reptiles to mammals to primates to apes to humans is our evolutionary history. And our connection to different families of animals, close and distant. We share a basic body plan, but have progressively invested more energy in offspring. Fish create countless embryos, then do little to help then to maturity. Frogs don’t look after their tadpoles, but reptiles start looking after their eggs. Mammals care for their young; called mammals because of breast feeding is needed by infants. Is this the origin of love?
I heard that the Earth has spent 85% of its 4.5 billion year life without any ice caps. But we live in an ice age, when there are polar ice caps. We are currently in a deglaciation period of the ice age, in contrast to some 15 thousand years ago (TYA) when the ice covered most of the earth. The ice has been progressively moving back, and today is doing so at an accelerated thanks to humanity’s contributions.
Unless humanity reduces the amount of energy it is burning, especially that coming from fossil fuel, it seems inevitable that we will soon have no more polar ice caps. What will be the effect of sea levels and shoreline. Literally unimaginable, in that these kinds of predictions are not really included in near-term scenarios.
If we expect a linear continuation of trends, we have plenty of time. Perhaps that explains why our efforts are still just to limit the rate of increase of greenhouse gas emissions; not even to reduce them. It assumes that the reserve of the Earth is infinite; that the oceans, the current store of the excess energy we put into the atmosphere can continue to store increasing amounts. Complex systems exhibit linear change up to a threshold when suddenly a totally different kind of change takes place. This is what some people mean they talk about the catastrophe of runaway climate change.
Positive and negative feedback loops are part of our biology and of the Earth itself. The former accelerates change, the latter prevents it. The emergence of Snowball Earth was driven by the spread of ice. This reflected back more sunlight energy, leading to lower temperature; and thus more ice. Now that the ice is melting, one side-effect is that it aggravates the heat retention, that water does much better than ice. Thus, further increasing the heat on Earth.
Imagine, you’re on the Titanic. You know that it’s heading for an iceberg that will sink it. All it would have taken was a small change of course, and accepting a slower time for the crossing. We have to stop burning fossil fuels or face a catastrophe for Earth. Can you imagine your world when the water is 5 to 10m higher? It could be as much as 60m when all the ice-caps are gone…
It was climate change that took our ancestors from the rain forests to the savannahs of Africa, where standing on two feet became more of an advantage. Climate changes over 100-year cycles in Africa selected for the ability to pass stories that would prepare future generations for the recurring cycles of drought and flood. Thus our brains allowed us to be adapted to more than one environment. And as modern humans emerged, were able to take over every corner of this Earth. No other species has ever done that; different species are selected for in different environments.
Since before the industrial, and even before the agricultural era, humanity has changed the planet. But it is only now that the scale of our capacity, in terms of total human population as well as the power of our technology are we now able to impact on the environment to make the Earth unliveable for humanity. Once the ice caps start melting, it becomes progressively harder to restore. I know they seem so distant; and that Earth will continue to thrive as a source of life; but what will be the fate of the humans?
So, let us first consider our history; and let us start at the first human transition in social organisation: from hunter-gatherer to agriculturist….in the next chapter of the 30. I also find this cartoon from XKCD a great way to quickly understand the change in temperatures, and that we are at the start of an exponential increase, as well human history.