One
point is how they treat CH4 as a greenhouse gas. In the short term,
methane is ~86 times powerful than CO2 as a greenhouse gas.
However, CH4 is more reactive and has a much shorter lifespan in the atmosphere than
CO2, or does it? Does methane deserve to be given a global warming
potential (GWP) of only 24 for climate modeling?
In
the atmosphere, methane is oxidized by OH- and Cl- radicals, while
CO2 is not. On the other hand, CO2 is converted by plants and algae
into O2 plus biomass. In aqueous environments, CH4 can be
produced and metabolized by various bacteria, at
material flows much greater than the “rate limited” atmospheric
oxidation process. On the other hand, CO2 is more soluble than CH4 in water, and thus CO2 can disappear out of the atmosphere into the oceans (and then reappear.) Thus, the actual amount of CO2 and CH4
in the biosphere is controlled by biological processes that
respond greatly to temperature, oxygen concentration, and other environmental factors.
However, the IPCC tends to be dominated by Atmospheric Chemists
and Computer Modelers that accord Biologists second class status.
In contrast, I tend to think in the terms of equilibriums controlled
by Equations of State, Gibbs Energy, and most importantly --
Biology. And everything published by the IPCC is reviewed by lawyers and governments that desire to avoid public panic.
If we consider solubility, then when equal pulses of CO2 and CH4 are added to the atmosphere, much of the CO2 will go into the oceans, so the actual near term effect of the residue of CH4 pulse in the atmosphere is on the close order of 260 times more powerful than the actual near term effect of the residue of the CO2 pulse in the atmosphere.
And, as we consider sequestration, we much remember that both CH4 and CO2 are in the oceans, and will come out as the partial pressure of these gases in the atmosphere decreases. As we plan to take greenhouse gases out of the atmosphere, we need to plan for the gas that will come out the oceans. Or, the biological processes in the oceans can convert either or both gases into biomass, thereby reducing their concentration(s) in the oceans, and causing the gas(es) to move from the atmosphere into the ocean. The ocean may be the easy path to sequestering carbon out of the atmosphere.
If
we look at the observed CH4 levels in the atmosphere
(http://www.esrl.noaa.gov/gmd/ccgg/trends_ch4/#global_data) we see
that the CH4 concentration in the atmosphere goes up, not down as
would be expected with a defined half-life on the order of 10 years.
Looking at the CH4 bump in the atmosphere after the oil well fires of
1991, there is a decline that looks to my eye like a higher partial
pressure in the atmosphere coming into equilibrium with the dissolved
CH4 in the oceans/wetlands. And, the bump in 1997, looks like higher
ocean temperatures from El Nino reducing the solubility of CH4 in the
oceans, so CH4 partitions into the atmosphere, then returns to the
oceans as cold, deep water is exposed.
Part
of the problem here is that many Environmental Scientists took
general chemistry and were taught that CH4 is “not soluble” in
water. In fact, CH4 is soluble in water at a few parts per
thousand. Thus, in the context of CH4 at a few parts per million in the
atmosphere, the oceans can and do hold a great deal of dissolved CH4 in solution, and the bacteria in
the oceans can produce a lot of CH4 as O2 concentrations diminish and temperatures rise.
(in the same way, green plants algae and bacteria can reduce large amounts of CO2 (e.g., CO2=> biomass + O2) , but
CO2 reduction is discounted by the IPCC.)
At
the surface, CH4 in the ocean is in equilibrium with the atmosphere (resulting in a very
small flux across the phase boundary). In deeper colder water, the
partial pressure of CH4 in the water is in equilibrium with the clathrates at the sea floor. As the world’s waters warm, CH4 will move
from the surface waters into the atmosphere, and clathrates will dissolve into the bottom waters. (Or, as we have started to
observe in the last 20 years, even release CH4 into the atmosphere.)
Anyway,
all of this means that we have to model CH4 in the atmosphere as if
the current concentration of CH4 will be in the atmosphere for
at least 20 years. Thus, the CH4 as equivalent CO2 is
~160 CO2e. Add in the real CO2 (405 ppmv), and greenhouse
forcing is currently 565 CO2e, yielding a forcing of ~ 3.6 W/m^2. Given
that permafrost and clathrates have already warmed enough to start
melting/decomposing, a climate sensitivity number as high as 3 seems
justified. That would indicate an expected temperature from global
warming at current conditions on the close order of 10.8C. That
is well above IPCC estimates. And, it is now! Waters that were in the
tropics 50 years ago, are releasing heat in the Arctic now.
Fifty
years ago, the forcing was only 2.6 W/m^2 (assuming CH4 GWP = 86),
while today, the tropic waters are forced at 3.6 W/m^2, and waters
that are in the tropics now, will be releasing that (38%
more) heat in the Arctic in 50 years.
Some
would object that the forcing formula is standardized for a period of
100 years. I would counter that with 560+ CO2e, over the next
20 years enough permafrost and clathrates will decompose to raise
greenhouse forcing to a much higher level. Over the longer term,
expecting the clathrates in the bottom of the ocean to remain solid
is like expecting the ice in your tea at a Houston, Texas BBQ party
to stay solid. As the tea warms, the ice will melt. As the
oceans warm, the clathrates will decompose. If we are seeing large scale clathrate decomposition 50 years, then there will be a great deal more CH4 in the atmosphere in the second half of the 100 year period, and this kind of senario is simply not recognized by the IPCC.
A
corollary is that polar ice will “melt” faster than the
current generation of models predict. I suggest that the older
ice flow models using Navier-Stokes/conservation
of momentum equations, miss the point that -- ice
near its melting point becomes highly discontinuous.
In particular, ice fractures can concentrate stress from large
volumes of ice into melt energy in tiny volumes at the propagating
edge of fractures.
Likewise, moulins and hydro-fracture processes disrupt “momentum”
ice flow models. Any model of ice at its melting point expressed in differential equations expressed in
differential equations will fail chaotically at the discontinuities.
And, we have reached the point where there is liquid water at both
the top and bottom of many ice structures meaning that top and bottom
surfaces are at their melting point/ discontinuities. Where there are
moulins and hydrofractrue events, the discontinuities extend through
the ice from top to bottom, and the ice models must fail. Ice
sheets do not have to melt in place. Now we know, that most ice
can “fall” into fjords or the ocean and float away. All
that it takes is enough warming to weaken the ice so that it fails
under the stresses imposed by the weight of the ice. My best guess on
sea level rise is meters in decades. NOAA has started to report
similar estimates.
(E.g., https://www.kcet.org/redefine/sea-level-rise-could-come-much-sooner-than-you-think , http://www.insurancejournal.com/news/national/2016/04/12/405089.htm ,
)
The
sea water advecting heat into today’s Arctic was warming in the
tropics, decades ago. Most of the heat in the biosphere is in
the oceans, but most climate scientists look at the temperature of
the atmosphere for a reading on the state of the climate. This
disregards the heat that goes into warming and melting ice.
This disregards the heat that goes into the oceans.
There
is a significant lag time in climate systems. We could stop
burning fossil fuels today, and it would be 50 years before warming
stabilized. We could stop burning fossil fuels today, and it would be
centuries before the sea floor clathrate and atmospheric methane
inventories stabilized. If oxygen levels in the oceans decline, then
the biomass in the oceans will be converted to methane, and the
equilibrium value for methane in the atmosphere could be high.
These are issues not addressed by IPCC models.
I
did computer modeling for Dr. Jay Forrester for the Club of
Rome Report that became Limits to Growth by
Meadows et al (1972). Much later, I wrote the Bechtel Risk
Management Manual as we considered the full range of very large
nuclear facility and hazardous waste site issues. We were
trying to price the decontamination, demolition, and waste disposal
projects being offered to us. For a long time, I kept a list of
the 300 worst things that could happen on large, long term projects,
such as the Hanford Waste Repository with its 100,000-year
design-life, and potential to contaminate the Columbia River with
hazardous and radioactive materials.
Along the way, I worked on a number of the worst hazardous waste
sites in the world, and did fate and transport analysis of how bad
stuff could affect populations; now, in the future, and in the deep
future.
Risk
actually has 3 components; Likelihood of the event, intensity
or damage from the event, and the likely timing of the event.
Life is a sequence of risks, and sometimes resources must be
allocated sequentially. For example, the sun will die, causing great
damage to Earth Bio systems, but that is in the deep future, and we
should address other risks first. Super volcanos and large
asteroids can inflict great damage, and are very likely risks in a time scale of a
million years, but AGW is a similar risk in the time frame of a few
of decades. We should address AGW first, so we will be around to worry
about super volcanoes as they will appear.
At
this time, the likelihood of AGW is near certain. (my estimate is 99.9999999%) Given the current concentrations of greenhouse gases in the atmosphere and oceans,
likely warming is almost certainly catastrophic for most animals over
4” in length. We have already seen more than a degree of AGW,
which means that water vapor in the atmosphere has increased and is
now acting as a greenhouse gas. This will warm the oceans faster,
lowering the solubility of CH4 and CO2 in the oceans, and increasing
the amount of greenhouse gases in the atmosphere. Thus, AGW is a
global risk, a catastrophic risk, a near certainty, and a very urgent
risk.
Weather
is a heat engine, and heat is fungible. All heat affects all
weather. All weather is affected by all heat. Attempts at
attribution are silly. The heat from AGW is in the system, and
is affecting all weather. It is in the nature of greenhouse
gases that as they heat the lower atmosphere, they cool the upper
atmosphere, making the atmosphere less stable and much more prone to
violent weather. And, cold air above warm moist air makes large
snow and hail storms more likely.
It
is very like the risk faced by the Elephant's
Child in Kipling’s story after the
Crocodile's musky, tusky mouth caught the Elephant's
Child by his little nose. At this time we
should take the Bi-Coloured-Python-Rock-Snake’s advice, and
immediately and instantly, pull as hard as ever we can, to avoid
being jerked into yonder limpid stream (by which I mean AGW) before
we can say Jack Robinson. Like the Elephant's Child, we have
been reckless
and naïve. We may survive, but like the Elephant's
Child, the effort required will stretch us, and change our outlook in every way.
http://www.boop.org/jan/justso/elephant.htm
cumulative and short-lived climate pollutants
Myles R. Allen
1,2
*
, Jan S. Fuglestvedt
3
, Keith P. Shine
4
, Andy Reisinger
5
, Raymond T. Pierrehumbert
2
and Piers M. Forster
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