1: Geoengineered safety
Population 9 billion
Global energy use 8 × 1020 joules
CO2 concentration 400 ppm, dropping
We acted early in the 21st century, invested aggressively in renewable energies and crucially, geoengineering
It wasn’t easy, but by investing heavily in R&D, we have built systems for sucking carbon dioxide out of the atmosphere and storing it underground. At the same time, we have invested in renewable energies and virtually weaned ourselves off fossil fuels. The net result: annual carbon emissions have plummeted, and atmospheric concentrations of CO2 are finally dropping.
Crucial to making this happen was the spread of bioenergy power plants coupled to carbon storage facilities – a soft form of geoengineering. We grew trees and plants to burn and produce electricity. They suck CO2 out of the atmosphere as they grow. We captured the greenhouse gases produced when we burn trees, and put the gases in geological seams deep underground – where they will stay for centuries or more.
Global temperatures have held steady since 2050. We’ve also halted the decline of sea ice in the Arctic and slowed ocean acidification. Sea levels are still rising, though, because of heat stored in the system from earlier emissions.
2: Slight delay
Population 8.5 billion
Global energy use 1 × 1021 joules
CO2 concentration stable at 550 ppm
We delayed both the transition to renewable energies, and the implementation of climate treaties
As a whole, we are a more efficient society than in 2013, using less energy and fewer materials to produce more. We are also good recyclers. All of this makes for better management of natural resources. Earlier on in the century, gas was the transition fuel of choice. Now most of our energy comes from renewables and nuclear. Incentives and better international institutions mean green technologies spread rapidly. We have made the transition to a low-carbon economy. We eat far less meat than in 2013, to cut the emissions generated by livestock farming. So pastures have shrunk and agriculture is more efficient. Forests are growing, boosting the amount of CO2 stored in trees around the world.
We live in compact cities with excellent public transport which also limits emissions. Although temperatures and sea levels have risen, some of the more extreme consequences of climate change haven’t come to pass.
3: Too little, too late
Population 9.5 billion
Global energy use 8 × 1020 joules
CO2 concentration 650 ppm and rising
We cut emissions, but not until late in the century
The first half of the century was spent mostly carrying on business as usual: we relied heavily on fossil fuels. We did not introduce any dramatic changes to our life styles or activities in terms of consumption, travel and the number of children we have. Then, towards the middle of the century, the consequences of climate change became too difficult to ignore. As a result, our governments slowly began introducing some unambitious policies to regulate emissions.
We are now slowly making our way towards a green energy supply. Oil consumption started to drop a few decades ago, but 75 per cent of our energy still comes from fossil fuels, not much less than the 82 per cent in 2011.
Because of our inaction, temperatures are still rising, as are sea levels. Models suggest they will continue doing so for several decades more.
4: Addicted to carbon
Population 12.5 billion
Global energy use 1.75 × 1021 joules
CO2 concentration 950 ppm and rising
The world economy is booming, but it’s fuelled by coal and oil. The global population continued to grow rapidly throughout the century, pushing emissions ever higher
Welcome to the globalised, high-tech, consumerist future: one where we are still hooked on fossil fuels. Emissions have gone through the roof, and human health and the environment are the casualties. Biodiversity crashes are threatening the normal operation of “ecosystem services” – natural processes such as water recycling through rain and rivers, and pollination.
Most of our energy still comes from fossil fuels, including from unconventional sources, like methane clathrates, tar sands, and fracked shale-gas deposits. Coal is still on the menu. We haven’t invested significantly in alternative energies. Globally, we also eat more meat and dairy products than we did in 2013.
Consequently, emissions and temperatures are still rising fast. Droughts and floods are more frequent and claiming more and more lives. Ocean acidification is severe, and getting worse. The Arctic has not had ice during the summer for several decades.
This article appeared in print under the headline “Pictures of Earth 2100”
Correction: When this article was first published on 3 October 2013, the figures for global energy use in the four scenarios were mistakenly formatted without superscripts.