Matthew Henry John Bartlett

Welcome to the first instantation of my NYR to summarise all the worthy nonfiction I read, in the hope that more of it will stick, not wash over me like knowledge off a duck’s back. Can you feel it? The personal development vibes are palpable! It’s the chapter “‘Sleeping giants’: surprises in the climate and Earth system” by Will Steffen, from Confronting Climate Change: Critical Issues for New Zealand, edited by Ralph Chapman, Jonathan Boston and Margot Schwass. So:

Science done since the IPCC’s Third Assessment Report in 2001 shows that global warming is likely to be in the upper range of IPCC estimates. Three areas contribute to this likelihood:

• Climate sensitivity: The effect of aerosol masking in the troposphere (the lowest part of the earth’s atmosphere) is uncertain. Aerosols include industrial polutants and smoke from wood fires, and work to some extent against global warming. We want to remove aerosols, as they are a health hazard, and as they’re removed their masking effect will go too, there may be a corresponding surge in warming global warming.
     Carbon cycles on land and sea are more complex than previously thought. Forest fires, for example, are likely to become more frequent in those parts of the world that are warming and drying, reducing the capacity of those areas to take up carbon from the atmosphere. Soil, which holds two-thirds of the carbon stored in land ecosystems, tends to release more of its CO₂ into the atmosphere if warmed.
• Cryospheric instability: The cryosphere is the frozen parts of the Earth’s surface. As the Artice ice sheet decreases (down 20% from 1973 to 2003), it uncovers more open water. Ice sheets reflect a lot of the sun’s rays, and the darker water absorbs a lot of them, so there is a positive feedback loop: the area is warmed, melting more ice, leading to greater warming.
     Recent measurements open up the possibility that the Greenland ice sheet may disappear into the sea (raising sea level by six metres) in centuries, rather than the previously-estimated millennia. Recent evidence also shows that the West Antarctic ice sheet (another six metres) may also be less stable than previously thought.
• Ocean acidity: Increasing CO₂ concentrations in the atmosphere mean the top layer of the sea absorbs more CO₂, becoming more acid in the process. Higher ocean acidity means phytoplankton with cacluim carbonate shells and coral reefs have trouble growing. The area of the ocean which is optimal for coral reefs has shrunk significantly in the last century or so. Given the IPCC mid-range CO₂ scenario, there will be no optimal areas left in the entire world by around 2065.