As the quantum of greenhouse gases increases, the average temperature also increases. This sets off other terrible effects. Weather patterns are disturbed leading to unseasonal massive hurricanes; average sea-level rises due to melting ice-caps, summers are hotter and longer, etc.
The chemistry was understood centuries ago. It was discussed as a possibility back in the 1820s by scientists like Joseph Fourier. Svant Arrehenius, who won the Nobel Prize for Chemistry in 1903, modelled the likely effects if you assume a doubling of the carbon dioxide in the atmosphere. The term itself was coined in the early 1900s. (Arrehenious is a distant ancestor of Thunberg).
Most technologies since the Industrial Revolution have been based on fossil-fuel. Burning fossil fuels releases carbon dioxide and other greenhouse gases. Accurate models of climate change effects caused by greenhouse gas emissions started being calculated around 50 years ago, in the 1970s. In scientific terms, those studies were remarkably accurate, given the multitude of variables. A new study says that, out of the 17 models released between 1970-2007, as many as 14 came close to predicting the effects visible now.
There is scientific consensus about the effects and every data point that we can measure suggests that things are getting worse. Average temperatures have risen, year on year. The melting of Arctic ice and glaciers everywhere is releasing trapped methane and other greenhouse gases, making things worse. A process of massive species extinction has started.
Fragile ecologies such as the Himalayas are likely to be devastated, along with the Arctic. As sea-levels rise, low-lying areas such as coastlines, and entire island archipelagoes will be submerged. India, with its vast coastline, is among the five nations most at risk from rising sea levels, and Bangladesh is also going to be badly affected.
If the average temperature rises by as little as 1.5oC, climate scientists reckon that 350 million people will be exposed to drought and at least 120 million will be pushed below the poverty line. This could happen as soon as 2030.
Sadly, scientific consensus doesn’t mean geopolitical consensus and the latter is necessary to take steps to retard this, leave alone reverse it. At the minimum, damage control requires emissions to drop at a compounded rate of 7.6 per cent every year until 2030.
This is theoretically possible, but it would require geopolitical consensus. Combating climate change not only requires new green technologies to be inducted at vast costs; this must happen everywhere. It would also require lifestyle changes that affect everybody. A move away from fossil fuels may lead to higher electricity and heating costs, and destroy highly profitable industries (coal, oil & gas, shipping, air transport) that employ many millions. In emerging economies, emission reduction may mean retooling entire economies dependent on cheap thermal power.
There are lobbies that oppose this. Apart from conventional energy industries, multiple politicians continue to deny that this is a scientific reality. This powerful lobby of political climate change deniers unsurprisingly, includes politicians in nations with highest greenhouse gas emissions, and in nations which are major fossil-fuel exporters. Donald Trump and Jair Bolsonaro have publicly disparaged Thunberg. Vladimir Putin has been dismissive.
But there have been some positive changes. More governments are taking the Paris Accord seriously, perhaps because the children of politicians have started lobbying parents. The UK has passed “zero-emission” legislation. The European Union is planning punitive taxes on imports from non-compliant nations. We’ll see this play out in the next few years. Greta and her generation might just have made enough of a difference to give the Earth a fighting chance.