• In the past 2000 years, during the Holocene temperatures varied a maximum of +/- 1 degrees
  • Over the past 150 years there was a stark increase in global temperatures
    • We already increased temperatures by over ~1 degree
  • If efforts to constrain emissions fail, the global average temperature by 2100 is expected to increase 3–5C (IPCC 2014) above pre-industrial levels.
    • Living with a temperature above 2C would be unknown terrain for humanity
  • our ability to mitigate climate change largely depends on our ability to not just reduce emissions, but also to ensure we rapidly reduce the harm to our natural carbon sinks  - and the biodiversity that upholds them (Earth carbon storage)

climate change is the quintessential market failure

Temperatures in the past 2,000 years

Emission Sources

From Paper - Our Future in the Anthropocene - Folke 2021

some 55% of global anthropogenic emissions causing global warming derive from the production of energy and its use in buildings and transport. The remaining 45% comes from human emissions that arise from the management of land and the production of buildings, vehicles, electronics, clothes, food, packaging, and other goods and materials (Ellen MacArthur Foundation 2019). The Food Systems itself accounts for about 25% of the emissions (Mbow et al. 2019). Human-driven landuse change through agriculture, forestry industry, and other activities (Lambin and Meyfroidt 2011) causes about 14% of the emissions (Friedlingstein et al. 2020).

Collectively, the top 10 emitting countries account for three quarters of global GHG emissions, while the bottom 100 countries account for only 3.5%(WRI 2020).

Second Order Effects

  • Melting of ice packs
    • Sea levels rise
    • Increased heat absorption by the Earth
  • Disruptions in food production
  • Higher risk of heatwaves and wildfires
  • Increased inequality (affecting disadvantaged populations most (Islam and Winkel 2017))

The climate and the biosphere interplay

Risk of Tipping point (nonlinear) effects increasing dramatically

  • The Earth’s resilience is decreasing

  • Science indicates that at the range of between 350 ppm and 450 ppm (of carbon dioxide) we have a risk of crossing catastrophic thresholds

  • 1.5 degrees target still poses substantial risks of irreversible change

“The 1.5°C target is one that science increasingly demonstrates is associated with substantial risk of triggering irreversible large change and that crossing tipping points cannot be excluded even at lower temperature increases (18)” Paper - Earth beyond six of nine planetary boundaries by Richardson et al 2023

IPCC August 21 Report

Link to Summary Report

Temperature Scenarios


B.2 Many changes in the climate system become larger in direct relation to increasing global warming. They include increases in the frequency and intensity of hot extremes, marine heatwaves, and heavy precipitation, agricultural and ecological droughts in some regions, and proportion of intense tropical cyclones, as well as reductions in Arctic sea ice, snow cover and permafrost B.5 Many changes due to past and future greenhouse gas emissions are irreversible for centuries to millennia, especially changes in the ocean, ice sheets and global sea level > upper ocean stratification (virtually certain), ocean acidification (virtually certain) and ocean deoxygenation (high confidence) will continue to increase in the 21st century, at rates dependent on future emissions. Changes are irreversible on centennial to millennial time scales > It is virtually certain that global mean sea level will continue to rise over the 21st century.

D 1.6 If global net negative CO2 emissions were to be achieved and be sustained, the global CO2-induced surface temperature increase would be gradually reversed but other climate changes would continue in their current direction for decades to millennia (high confidence)

Created on: 2021-01-08 Inspired by: Course - Planetary Boundaries Related: Planetary Boundaries