by Matt Owens February 4, 2013
New research shows that of an estimated 550 GtC (gigatonnes of carbon) previously modeled to be stored in soil, leaf litter, and plant biomass between 1860 and 2100 (using the leading climate models to run the A1B scenario of emissions), 25%, actually won't be. This equates to 14 additional years worth of human emissions at 2012 rates being injected into the atmosphere over the coming years. This process is already happening, like in England. Baring a deus ex machina discovery about the climate system, this latest finding is confirmation of some of our worst fears. The worst-case scenarios, the old A1FI and the new RCP8.5, can now be said to be very likely, if not all-but guaranteed. The damage and destruction from either scenario could easily approach or exceed that of a global nuclear war by 2100. As bad as this sounds, things can always get worse.
Instead of getting absorbed by the soil-plant system, 137.5 GtC will be left in the air. Some of that CO2 will move into ocean waters, but probably only about 1/3 of it. Currently, 26% of human carbon emissions are going into land sinks, but over the course of the coming years, that number will steadily drop. This extra carbon along with other soil feedbacks now being estimated, could lead to enough additional warming to actually push total warming by 2100 from the A1B scenario into (or above) the worst-case scenario of A1FI.
There have been a growing number of studies pointing in this direction. This latest research was several years in production, and the results were published only in 2012, in the journal Biogeosciences. Daniel Goll of the Max Planck Institute led an international team to accomplish the work.
The team's work shows that phosphorus and nitrogen limitations in soils around the world will actually make plants unable to use as much carbon dioxide as has been assumed in global climate models - at least up until now. Brace yourself for some much scarier looking model forecasts.
Instead of continuing to add more and more mass, plants around the world will plateau. Or for other climate reasons (i.e. high temperatures) they will decline in primary productivity. Primary productivity is a term used for the amount of growth (productivity) by plants/via photosynthesis.
This principle of nutrient limitation is simple: all organisms need a certain baseline ratio of elements to grow and maintain their cells and keep their metabolism going; increasing just one nutrient doesn't do any good for a plant if it still needs other nutrients.
Estimating nutrient limitation's effect was complex, and time consuming however. Available nitrogen and phosphorus had to be estimated for the entire surface of the planet, and those values vary substantially based on local soil characteristics. And, to a certain extent they vary over time based on local climate.
Global climate models have barely taken into consideration this nutrient limitation, if at all. The new research shows that they are making large errors in carbon flows from the atmosphere to the land. In fact, the published paper by Goll et al. shows that under the A1B scenario, after adjusting for the new information, the nutrient limitation alone will cause 137.5 GtC less carbon than expected to be absorbed by plants. This is huge considering that human emissions have reached all time highs of around 10 GtC per year most recently. And this isn't all.
The A1B scenario (which is now being phased out for a new set of climate emissions pathway scenarios, the RCP scenarios) represents a reduction in emissions growth and fossil fuel use growth by 2100. This reduction in fossil fuel use has been considered the most likely by some people, based on economic factors associated with fossil fuels. Namely: increasing extraction costs and decreasing supply, which are theorized to reduce usage.
There are several flaws in this theory however. Reduced use will cut demand and thus decrease free-market pricing of the commodity. Lower prices means an increased incentive to continue using. Likewise, the adoption of alternative energy sources, like solar and wind, also reduces upward price pressure on fossil fuels. And, costs of extraction have been going up for a long time now, but new technology has come along to reduce those costs.
Of course, there is a limit on the amount of fossil fuels in the ground. But, those limits are far from being reached for coal, the primary source of carbon dioxide emissions. And for oil, new, hard-to-reach sources, like the Canadian tar sands, are being brought online as we speak. So while some limits are already being felt, those limits are still very far away for coal, and new technologies are stretching our use of liquid fuel further and further, making us more and more productive on the same gallon of oil, but not reducing the actual total global consumption.
All this is to say that the A1B scenario expects major voluntary reductions in fossil fuel use, so that use will be below what the free-market would otherwise dictate. The worst warming scenario has been the A1FI scenario (now being phased out for the similar RCP8.5 scenario), which showed a warming of about 4.7°C (8.5°F) by 2100 compared to the pre-industrial period. The A1B scenario (now roughly equal to the RCP6.0), which showed a warming of about 3.4°C (6.1°F) by 2100, was considered moderate. But adjusting for the new numbers from this study and a growing list of others relating to similar refinements in understanding means that the emissions assumptions of the A1B scenario could end up producing warming results well into (or above) the A1FI worst-case scenario.
If the people of the world continue with business as usual, this suicidally increasing emissions rate won't stop according to the A1B emissions assumption, but instead it will grow into the A1FI scenario - and this additional warming will be even worse. Once the soil-plant carbon sink is full, adding more CO2 isn't going to unclog it. And the other soil-carbon effects are likewise amplified with rising temperatures and CO2 levels, so they will increase in severity as well.
Other parts of the soil equation include releases from warming permafrost and northern peat fields, an area of very high concern. Thawing soils could contribute even more CO2 to the air, as well as methane and nitrous oxide, all major greenhouse gasses. In fact, the northern thaw effect could eclipse the nutrient limitation adjustment by far. Some researchers think that sufficient volumes of methane could be released to push global warming ahead by several decades in just a few years.
Backing up these concerns is an interpretation of the paleoclimate record which shows that the equilibrium temperature for Earth with this much CO2 in the air could be far higher than models are now predicting. The discrepancy indicates that something large is be missing from the global climate models. Possibly something much larger than even this new finding. Permafrost is a leading contender to plug that hole. Methane hydrates on the bottom of the shallow Arctic Ocean, and at other shallow ocean locations, could also play a major role. But there are additional possibilities, like increased wildfire, desertification, and forest die-off.
Paleoclimate records also show that climate has shifted abruptly over just a few decades in the direction of warming, while taking longer to move in the opposite direction: cooling. So it appears that the climate system is inherently primed for fast moves to warmer states. Based on the forcings now impinging on the planet, it is logical that abrupt changes are possible, and will happen (Pitman and Stouffer, 2006).
It is now clear that global warming is on track to cause serious damage around the world; including a permafrost carbon feedback could add several more degrees to warming. This means that if the people of the world take serious, meaningful action, and reduce CO2 emission every year, starting now, there could still be a very serious warming by 2100. This is a major problem, and many cities around the world will face harsh realities.
If temperatures climb to A1FI (or RCP8.5) levels or beyond, many cities will be destroyed. Some will be abandoned to encroaching desert. Others will be physically destroyed by storms of unprecedented severity. Some places are already on the way to running out of water, and those water pressures will get worse. Meanwhile, the background threat of a meter or more of sea level rise (by 2100) threatens coastal development everywhere. In spite of these challenges, inaction on carbon pollution could make things much worse yet.
Despite these challenges, giving up or becoming despondent in despair is not acceptable.
In light of these climate realities, governments around the world march forward, blindly smiling at fossil fuel interests while tossing a few dollars to the solar and wind industries. The US federal government is now spending $711 billion per year on a growing defense budget while at the same time spending on renewable energy has dwindled, and is projected to hit $11 billion by 2014.
This is so outrageous, and the media today is so full of hyperbole, that words fail to capture an appropriate response. In essence, this is like a willfully negligent poisoning of the entire human race, and for many (possibly all) generations to come. The climate effects will not be partly good and partly bad as some have said. They will be very bad. And everyone will suffer, directly or indirectly. No man is an island.