The problem: rising carbon dioxide in the atmosphere
The level of carbon dioxide, the main greenhouse gas, has been rising since the Industrial Revolution and is at its highest in about 4m years. The rate of the rise is even more striking, the fastest for 66m years, with scientists saying the world is in “uncharted territory”.
The causes (I): burning fossil fuels
Billions of tonnes of CO2 are still pumped into the atmosphere every year from coal, oil and gas burning. The slight reduction in 2020 as a result of coronavirus lockdowns was no more than a “tiny blip”, and emissions have since resumed their upward trajectory.
The causes (II): forest destruction
The felling of forests for timber, beef, soy and palm oil is a big contributor to CO2 emissions. It is also a significant cause of the annihilation of wildlife.
The causes (III): methane emissions
Methane is a potent greenhouse gas and causes 25% of all global heating today. Fossil fuel extraction, cattle, rice paddies and landfills are responsible. There has been a “scary” surge in methane emissions since 2007, according to scientists, potentially due to wetlands heating up.
The consequences: global temperature rise
The planet’s average temperature started to climb steadily two centuries ago and has rocketed since the second world war as consumption and population have risen. Many records were smashed in 2023, which will be the hottest year on record. Global heating means there is more energy in the atmosphere, making extreme weather events more frequent and more intense.
The consequences: rising sea levels
Sea levels are inexorably rising as ice on land melts and hotter oceans expand. Sea levels are slow to respond to global heating, so even if the temperature rise is restricted to 2C above pre-industrial levels, one in five people in the world eventually will experience their cities being submerged, from New York to London to Shanghai.
The consequences: shrinking Arctic sea ice
As heating melts the sea ice, it reveals darker water that absorbs more of the sun’s heat, causing more heating – one example of the vicious circles in the climate system. Scientists think the changes in the Arctic may be responsible for worsened heatwaves and floods in Eurasia and North America.
The upside (I): wind and solar energy is soaring
Huge drops in cost have helped renewable energy become the cheapest electricity in most places and the exponential growth is expected to continue. But action and support is still required to reach the scale needed, especially in developing countries.
The upside (II): electric vehicles
The global fleet of electric cars and vans is still small compared with those vehicles running on fossil fuels. But sales are growing extremely quickly and tipping points for EV adoption have already been reached in several countries. Electric cars are cheaper to own and run, suggesting they will replace combustion engine vehicles.
The upside (III): battery costs
Plummeting battery costs not only increase electric car sales but can enable renewable energy to be stored while the sun is shining and the wind blows. But other technologies with longer storage duration, such as green hydrogen, will also be needed.
• Cop28: Can fossil fuel companies transition to clean energy?
On Tuesday 5 December, 8pm-9.15pm GMT, join Damian Carrington, Christiana Figueres, Tessa Khan and Mike Coffin for a livestreamed discussion on whether fossil fuel companies can transition to clean energy. Book tickets here or at theguardian.live
