Climate has again come to the fore as the Prime Mover of sorts. The world is getting warmer. This time, it is man-made. Hence, a new name has been penned to mark this distinction – the Anthropocene, which is markedly different from the Holocene. During the Anthropocene, humans have caused great changes to their ecologies by forcing atmospheric changes. They emitted enormous amounts of greenhouse gases into the atmosphere. These gases trap solar heat that should have escaped to space. However, one should not overlook the importance of greenhouse gases for planetary reasons. The Moon has a surface temperature of (negative) -16 Celsius because it has no atmosphere and hence no greenhouse gases. If the Earth didn’t have any such atmosphere and greenhouse gases, especially water vapor, it would have a similar surface temperature as the Moon. This is clearly not the case. Thanks to the presence of appropriate amounts of greenhouse gases in our atmosphere, our Earth has a pleasant atmosphere and a comfortable temperature of, on average, +15 Celsius. Without this arrangement, Earth would have been unhabitable.
But too much of greenhouse gas is also bad, and we can see that example in our very own Solar neighborhood. Venus, our next-door neighbor in the Solar System, has a runaway greenhouse effect: it has a very dense cloud that reflects solar radiation from cloud-tops while beneath the clouds it is a hothouse. Huge amounts of greenhouse gases have filled the surface that makes the surface temperature of Venus skyrocket to about 475C, which melts even metals like lead. The Nature shows us a great truth: too much of anything is bad. There is a delicate balance to sustain life, ecology, and intelligence. Since Earth sustains such a balance, it is sometimes called a Goldilocks’ planet.
Goldilocks, as the famous children’s fable goes, is a blonde girl who lost her way into the forest. She found a small cottage in the woods, dared to go in, and found to her surprise everything in three varieties. One of the varieties was extreme to one end, the other extreme to another end and one in the middle of the two extremes. For example, she found three porridge bowls – one was very hot, one was too cold, and the third was just right. She found three beds- one was too hard, one was too soft, and the third just right. This parameter -‘just right’ – is so applicable to planet Earth that people are now forced to think about the possibility of ‘habitability’ and ‘rarity’ of life and intelligence in the Universe these days.
There are certain cosmic conditions upon which biological life depends. A planet can harbor life if it has a mid-sized dwarf star that shines for a very, very long time (i.e. billions of years) with some stability. Additionally, the stellar neighborhood should have some richness of heavy elements, and the planet needs to be heavy enough to retain a magnetosphere and atmosphere and should have tectonic activity, etc. A suitable distance from the star is also mandatory so that water could be found in all three stages – ice, liquid and vapor phases. This is known in astronomy as a ‘habitable zone’. On such a planet, life could thrive. But the rise, spread, and longevity of intelligent beings on such a planet is altogether a different matter. Scientists are invoking Gaian Bottlenecks, Hansonian Great Filter, and Rare Earth hypotheses to explain why a Goldilocks condition is necessary for intelligence to prosper.
Let us go back to Carl Sagan (1934-1996) and his great prose where he romanticized an image that the Voyager-I spacecraft took on the 14th February of 1990 – the ‘pale blue dot’ image of the Earth from the outskirts of Saturn. In that small speck of bluish speck, all of mankind lives. In the immensity of space, that is a very insignificant point, but to us that one dot is hugely important because that is our home, and we have nowhere else to go, at least in this Solar System. If we discover interstellar space travel technology, and we live to see to that, then perhaps we could be bold enough to vie for nearby stellar neighborhoods to look for suitable Earth-like Goldilocks planets and settle there. But till then, that tiny pale blue dot is the only planet for us to live.
This brings us to our existential question related to climate change. There is a story about Easter Island located in south-east Pacific. Easter Islanders erected large statues as part of their clan competition and religious activities. As a result of this unsustainable competition, the island resources depleted quickly. The islanders took down big trees, depleted fish habitats in their nearby sea, and the human population increased. Then the inevitable happened. The island was located in such a geographical location that resulted in very low amounts of precipitation. When the islanders fell down the trees, the island did not get enough time to grow further trees as rainfall was limited, and human greed was unabated. As a result, the islanders faced drought, famine, and disease, which decimated their population drastically. The islanders had nowhere to go in their vicinity, so internecine fights broke out that further declined their population. Once a rich island of enough biodiversity stands now as semi-arid island with no or few visible big trees, and only big statues which no one valued anymore. The Easter Island stands out as a strong simile to what may befall our planet. If we humans continue to destabilize the planet in such wanton manner, we would run into a similar disaster.
Currently, we do not pay sufficient attention to planetary ecology and biodiversity, which are essential to our food and living. Our carbon footprint is large. We are pumping huge amounts of greenhouse gases into the atmosphere. Our temperatures are rising, and large swaths of land in the coastal region will get submerged in rising seas. That will displace millions of people and will create climate refugees, which in turn will destabilize countries and regions. Not only that, rising temperatures will push certain tipping points to fall in a way that will destabilize the planet. For example, if Greenland’s ice melts, the sweet water will change the salinity of the northeast Atlantic so that the Gulf Stream, the big ‘conveyor belt’ carrying heat to the north-west coast of Europe, may stop. That will bring the ‘snow line’ further south of Europe, meaning a lot of countries will be under snow during winter times. Currently, Canada and the Great Britain have different weather, although their latitudes are close, because the Gulf Stream brings warmth to the coast of Britain. This will change, however, and once changed, it will take a very long time (probably millennia) for it to switch back. Such changes behave like a threshold which, once crossed, will not retort to previous equilibria.
We live in this one planet having nowhere else to go in this Solar System; we cannot wholesale migrate to any other planet or moon as none are habitable for us. We have started and caused a sixth extinction which is currently in place. If we do not stop now, our planet will fail to sustain us. In the end, the doom will be on us. People of Bangladesh, where I live now, are facing the brunt of climate change in many ways – some are subtle (increasing salinity, decreasing fishery, change of fish habitat, erosion) and some are direct (increasing flood frequency, tropical cyclones, increasing water logging in coastal areas). The beautiful retreat island of Maldives will be totally lost to sea. New York will face increasing storm surges. Soon, people from Bangladesh and people from New York won’t be too different; they will both face problems from Nature, caused by a similar set of activities set by humans.
You see, climate change is a great leveler indeed.