Awareness by podcast

My 7 December 2023 interview on The Why? Curve podcast aimed to raise awareness of the need for smarter investment in climate change mitigation to prevent major Earth systems breaking down in the 2050s or 2060s. Worse, there are reasons to think that the loss of Arctic summer sea ice from around 2030 could accelerate this process dramatically. These risks are so obvious and dire that they call for urgent precautionary action.

Cascades of chaos

Major Earth systems are becoming unstable under stress from global heating and other more direct pressures. These systems include the Arctic Ocean and its surrounding coasts and permafrosts, the Amazon and other rainforests, and major ocean currents and monsoons. They have been absorbing stresses for decades but are now approaching the limits of their tolerance. That limit is each system’s tipping point, when it becomes committed to chaotic transformation. Because Earth systems are connected they can pull each other over, so multiple systems could become committed to breaking down at about the same time. This would be a ‘biosphere-wide tipping point‘ (BTP), which is a key moment because we can influence outcomes until it is reached, but we will be powerless to do so afterwards.

Deadline awareness

Time for a re-think

The idea of a BTP challenges all our assumptions about the future. These were shaped during centuries of economic expansion into what was seen as an infinite global frontier. But our predicament now, at the end of that phase, leads us towards the idea of deadline-aware mitigation investment (DAMI) with a new purpose and a new approach.

• The new purpose would be to postpone the BTP, thus buying ourselves time to strengthen our societies against climate chaos, decarbonise our economies, recapture GHGs from the air, and restore peace with nature.
• The new approach would be to refocus investments on those that are proven to reduce net GHG emissions soonest and most cost-effectively, while remaining true to our other values.

Postponing the BTP

I have proposed and demonstrated a transparent and consistent way to calculate the cost-effectiveness of different mitigation investments in postponing the BTP. This relies on:

• assuming a realistic date for the BTP;
• calculating the amount and timing of net GHG emission savings from each mitigation investment up to that date (in tCO₂e);
• valuing those savings exponentially more highly the sooner they are delivered relative to that date, to give us the ‘dated mitigation value’ of each investment (in tCO₂edmv); and
• estimating true mitigation cost-effectiveness from the cost of the project over the same period (in tCO₂edmv/£).

DAMI useful

Armed with data on true mitigation cost-effectiveness, public servants can reliably choose the best public investments. This would improve governments’ ability to deliver on their ‘net zero’ or Paris Agreement goals. Taxes and other regulatory signals can also be adjusted to ensure that the most cost-effective mitigation projects attract the highest rates of financial return for private investors, while also valuing healthy ecosystems, biodiversity, human rights and other important co-benefits.

The Arctic threat

Summer sea ice decline

The progressive thinning and shrinking of Arctic Ocean sea ice since 1979 was first flagged by Peter Wadhams, former Director of the Scott Polar Research Institute, in his 2016 book A Farewell to Ice. The volume of Arctic summer sea ice continued to decline and is now expected to approach zero at its September minimum by around 2030.

Heating oceans

The context for the Arctic issue is the rising heat of the oceans. This has increased by hundreds of zettajoules (ZJ) since the mid-1980s (one ZJ ≈ double humanity’s current energy use). This is where most greenhouse heat has been going, with much of the rest going into melting ice.

Step-change in Arctic heating

Without summer sea ice to absorb excess heat, at least two mechanisms mean that the temperature of the Arctic Ocean and its seabed and coastal zone will begin to rise much faster than before. These are:

• that it takes 80 times less heat to warm water than to melt ice (4 J/g/C for water [due to its ‘heat capacity’] vs 334 J/g/C for ice [due to its ‘latent heat of fusion’]); and
• that without white and reflective ice, more solar heat enters the ocean.

Potential methane consequences

The likely rate at which Arctic Ocean temperature will rise under ice-free summer conditions is unknown, but could be high. Until we know what will actually happen, a precautionary attitude is called for since sudden Arctic heating could have the following consequences:

• a potentially large share of many hundreds of billions of tonnes (Gt) of peat contained within permafrosts throughout the Arctic will decay and release methane (CH4); and
• a potentially large share of the hundreds of Gt of CH4 contained within frozen clathrates (or hydrates) in the Arctic seabed will be released.

Potential climate consequences

Every tonne of methane is about 86 times more potent as a GHG over 20 years (the most relevant timescale) than a tonne of carbon dioxide (CO₂), so 1 Gt CH₄ ≈ 86 GtCO₂e, equivalent to about twice current global emissions of all GHGs put together. If there’s the slightest chance of this happening, urgent precautionary investment to mitigate harm would be justified. Since we cannot now prevent the loss of Arctic summer sea ice, this may have to involve open-air methane recapture. If we need to do this in the 2030s, we should start thinking about it now.

What is to be done?

As a contribution to safeguarding the process of urgent, fair and effective decarbonisation, my podcast aimed to raise awareness and encourage urgent, practical thought:

• about the BTP deadline, to encourage greater cost-effectiveness in mitigation investment, so that everything we do contributes to postponing the BTP;
• about the Arctic methane threat, to alert people to the need for precautionary action to make sure that we don’t sleep-walk into an early BTP; and
• about both, to encourage anyone who can to spread the word, the sense of urgency, and the need for a new spirit of ecological realism in all our actions.

Julian Caldecott 2023