Arctic News: social cost

Sunday, March 7, 2021

Confirm Methane's Importance

Agriculture, land use and forestry responsible for half of people's greenhouse gases emissions?

The image on the right updates an image from an earlier post, illustrating the difference between using a Gobal Warming Potential (GWP) for methane of 150 over a few years versus 28 over 100 years. The IPCC in its special report Climate Change and Land assessed the impact of AFOLU (agriculture, forestry, and other land use) versus the impact of fossil fuel, etc., by using a GWP for methane of 28 over 100 years, referring to AR5, an earlier IPCC report.

Since AR5 was published, a study found methane's 100-year GWP to be 14% higher than the IPCC value. The image on the right therefore uses a short-term GWP for methane of 171 in the panel on the right-hand side, 14% higher than the 150 used earlier.

When using this 171 GWP for methane and when including pre- and post-production activities in the food system, AFOLU (agriculture, forestry, and other land use) causes about half of people's 2007-2016 emissions.

The black bar for methane at a GWP of 171 in the panel on the right-hand side further shows a far greater impact caused by fossil fuel, etc., in particular by the use of natural gas for heating buildings, generating electricity, etc.

Methane's one-year GWP is 200

The image below shows a trendline that is based on IPCC AR5 data that were similarly updated by 14% and that indicates that methane's one-year GWP is 200.

Methane Levels Rising Rapidly

NOAA data show that methane's global mean for November 2020 was 1891.9 ppb, i.e. 16.3 ppb above the 1875.6 ppb global mean for November 2019.

Social Cost of Methane

In a January 2021 executive order, President Biden called - among other things - for an update of the 'social cost of methane', to take account of climate risk, of environmental justice, and of intergenerational equity, and to have a dollar figure for agencies to use when monetizing the value of changes in greenhouse gas emissions resulting from regulations and other relevant agency actions.

Of course, it should be painfully clear by now that the unfolding climate collapse is an existential threat, making it obviously and vitally important to act on methane. We simply cannot afford to delay action, we cannot afford to do so financially nor in any other way. So, what can and should be done?

Above suggestion to take strong action was posted Nov. 9, 2020 at facebook

Even when issuing a mandate, e.g., for a rapid transition to clean, renewable energy, the question remains how this is best implemented. To what extent could bans help speed up the necessary transition to clean, renewable energy? Examples are banning cars from entering (parts of) cities, banning the construction of new coal-fired power plants, banning fracking and banning natural gas hookups in new construction.

Image from the 2014 post Biochar Builds Real Assets

The Climate Plan likes local communities to decide what works best in their area, while recommending local feebates as the preferred policy tool. Indeed, fees that are set high enough can effectively ban specific alternatives. Furthermore, instead of using money, local councils could add extra fees to rates for land where soil carbon falls, while using all the revenues for rebates on rates for land where soil carbon rises; that way, biochar effectively becomes a tool to lower rates, while it will also help improve the soil's fertility, its ability to retain water and to support more vegetation.
That way, real assets are built.

We cannot afford to delay action

Mean global carbon dioxide was 413.28 ppm in November 2020. Mean global methane was 1891.9 ppb in November 2020, which at a 1-year GWP of 200 is 378.38 ppm CO₂e. Together, CO₂ and methane add up to 791.66 ppm CO₂e, which is 408.34 ppm CO₂e away from the 1200 ppm CO₂e clouds tipping point.

This 408.34 ppm CO₂e translates into a methane equivalent of 2042 ppb of methane (again using a 1-year GWP of 200), in other words, it would add about 5 Gt of methane, an amount similar to the methane that is aready in the atmosphere now.

Such a methane burst of about 5 Gt alone could suffice to raise the CO₂e level to 1200 ppm and trigger a further 8°C global temperature rise due to the clouds feedback.

How likely is a large methane burst? Remember the warnings by Natalia Shakhova et al., who more than a decade ago concluded abrupt release of up to 50 Gt from the vast amounts of methane stored in the form of hydrates and free gas to be highly possible at any time. A recent study found methane leaking from a large pool of deep, preformed methane, indicating a large potential for abrupt future releases.

Keep in mind that the clouds feedback could also be triggered with a much smaller methane burst, since such an event would also come with a collapse in industrial activity and the associated fall in sulfate cooling, numerous additional feedbacks, and huge rises in greenhouse gas emissions, next to the temperature rise due to such a methane burst itself. The total potential rise in global air temperature at land-ocean surface level from 1750 to 2026 could be 18°C when including the clouds feedback. Also keep in mind that humans will likely go extinct with a 3°C rise and most life on Earth will disappear with a 5°C rise.

High peak levels

Ominously, some very high peak levels were recently recorded by the MetOp-1 satellite in the afternoon at 469 mb, i.e. 2930 ppb on March 3 and 2878 ppb on March 4.

As discussed in an earlier post, next to seafloor methane, there are further warming elements that could contribute to a rapid acceleration of the temperature rise.

Conclusion