Mass Extinction
There has been 5 mass extinctions in the last 500 million years.
We are now in the 6th.
251.9 mya – The End-Permian mass extinction: 90% of life went extinct due to carbon dioxide from Siberian volcanoes over several thousand years that increased temperatures by 10°C
50,000 to 10,000 years ago – The Late Pleistocene to Holocene Megafauna extinction: 80% of mammals weighing greater than 1,000kg went extinct, due to human activity & climate change
Habitat Loss
1 billion hectares of forest were lost in the 20th century.
At least 70% of global land area is impacted by human use:
Pasture 37%
Commercial forestry 22%
Crops 12%
Barren/rock 12%
Forests (unmanaged) 9%
Unforested ecosystems 7%
Infrastructure 1%
source: The Land Gap Report, 2022; IPCC 2019
Around 1900, 8m square km was used for agriculture
By 2000 this was about 15m square km
Population Growth
Between 1945 & 2000 the number of people in the world tripled
2025: 8.2 billion
Global Warming (Sea levels, Glaciers, Weather Change)
About 500 billion tonnes of carbon have been emitted from our burning of fossil fuels
Carbon dioxide levels in the air are >50% higher than pre-industrial times
2025: 430 ppm (275ppm pre industrial revolution)
The global average temperature for the most recent 10-year period, from 2014 to 2023, is estimated to be the warmest 10-year period on record, at around 1.2°C above the 1850-1900 average (WMO)
3 million years ago temperatures were 2.5°C above pre-industrial levels.
Higher temperatures mean increased frequency of droughts, storms, floods & heatwaves.
2015 Paris Agreement set a target of 1.5°C above pre-industrial levels.
IPCC estimates global warming will reach 3.2°C by 2100.
Transport is responsible for about one quarter of CO2 emissions that come from burning fossil fuels.
2021: 95% of transport was oil dependent.
Half of all aviation emissions are caused by 1% of the world’s population.
80% of the world’s population have never flown.
CO2 emissions between 1850 & 2021:
USA – 420 Gt
China – 242
Russia – 117
Germany – 93
UK – 75
Japan – 67
India – 57
France – 39
Canada – 34
“To stay in line with our international climate targets we need to get our individual per capita emissions down to somewhere around 1 tonne of carbon dioxide a year…US is 17.1, China 6.6.” Greta
Kaya Identity: total carbon emissions = per capita income, total population, the energy intensity of economic output & the carbon content of economic output.
The richest 10% are responsible for about half of all.
About 100 corporations are responsible for over 70% of global civilian (as opposed to military) carbon emissions. And 20 of them for about one-third.
Emissions are under reported by 16%-23%.
Methane emissions have increased 2.6 times in the last 200 years.
CO2 versus Methane:
80% of methane emitted is removed via chemical reactions in 20 years, & after 40 years is virtually all gone.
For CO2 after 40 years 50% still remains, & 20% remains for 10,000 years.
It has to be absorbed by land & ocean sinks, as it is not removed by chemical reactions.
CO2 is responsible for around 90% of additional warming in the 21st century.
Rising CO2 levels causes ocean acidification & loss of coral reefs
Sea levels have risen about 20cm since 1900.
By 2100 forecast: 50cm to 2m
Tipping points:
1. Antarctic ice sheet
2. Greenland ice sheet
3. Artic sea ice
4. Permafrost
5. AMOC (Atlantic Meridional Overturning Circulation)
6. Amazon rainforest
60% of Russia is permafrost
AMOC has slowed by about 15% since 1950, hence the North Atlantic is the only region in the world that has cooled since 1900.
Agriculture & Fisheries
96% of mammals are humans or livestock reared for humans,
& 70% of birds are poultry, mainly chickens (FT, 09/03/21)
Nitrogen fertilizer use has increased 10 fold since the 1960’s.
Water
Soil
The world’s soil contains about 4 times the amount of carbon as in the atmosphere & all plants combined.
Pollution
2016: 11m tonnes of plastic dumped in the ocean
Biggest plastic polluters:
Coca-Cola
Nestle
Unilever
Proctor & Gamble
USA is the highest producer of plastic waste per person; UK second