Global warming and how it will affect soil carbon

Two millennia of mean surface temperatures according to different reconstructions from climate proxieseach smoothed on a decadal scale, with the instrumental temperature record overlaid in black. Multiple independently produced datasets confirm that from to the global average land and ocean surface temperature increased by 0.

Global warming and how it will affect soil carbon

References The main potential changes in soil-forming factors forcing variables directly resulting from global change would be in organic matter supply from biomass, soil temperature regime and soil hydrology, the latter because of shifts in rainfall zones as well as changes in potential evapotranspiration.

Soil changes because of a potential rise in sea level resulting from a net reduction in Antarctic ice cap volume and ocean warming are discussed in Brammer and Brinkman and are summarized at the end of this paper.

The biggest single change in soils expected as a result of these postulated forcing changes would be a gradual improvement in fertility and physical conditions of soils in humid and subhumid climates.

Another major change would be the poleward retreat of the permafrost boundary, discussed by Goryachkin and Targulian Other widespread changes would be in degree rather than in kind. Certain tropical soils with low physico-chemical activity, such as in the Amazon region, may undergo a radical change from one major soil-forming process to another Sombroek,as discussed below under Processes in soils.

The changes in temperature but particularly in rainfall to be expected as a result of global warming are subject to major uncertainties for several reasons.


Different global circulation models do not lead to mutually consistent results an example for Europe is given by Santer,and they are not yet adequately verified. Also, the interaction with changes in location and intensity of major ocean currents and resultant possible modifications in sea surface temperatures is still most uncertain, as well as the interaction with possible major changes in cloudiness and land cover and the resulting changes in albedo and actual evapotranspiration.

Indirect effects of climate change on soils through CO2-induced increases in growth rates or water-use efficiencies, through sea-level rise, through climate-induced decrease or increase in vegetative cover, or a change in human influence on soils because of the changes in options for the farmer, for example, may well each be greater than direct effects on soils of higher temperatures or greater rainfall variability and larger or smaller rainfall totals.

Possible changes in forcing variables With these caveats, one could stipulate the following changes in forcing variables as likely to materialize sometime during the next century: Peak rainfall intensities could increase in several regions.

This paper will not touch upon a possibly increased frequency and severity of cyclonic storms in the present cyclone belts or conceivable poleward widening of these belts because of increased sea surface temperatures, which would also give rise to greater frequencies of high-intensity rainfall events.

Effects of higher CO2 on soil fertility, physical conditions and productivity Higher atmospheric CO2 concentration, as discussed in subsequent chapters, increases growth rates and water-use efficiency of crops and natural vegetation in so far as other factors do not become limiting.

The higher temperature optima of some plants under increased CO2 would tend to counteract adverse effects of temperature rise, such as increased nighttime respiration. The shortened growth cycle of a given species because of higher CO2 and temperature would be compensated for in natural vegetation by adjustments in species composition or dominance.

In agro-ecosystems the choice of longer-duration cultivars or changes in cropping pattern could eliminate unproductive periods that might arise because of the shorter growth cycle of the main crop. There will be adequate time to adjust to the changes since these are expected to occur over decades, rather than years or days as in all present experimental situations.

This chapter deals with the effects of gradually rising CO2 concentrations as observed in the recent past and stipulated in simulation models that apply transient scenarios. As summarized in Figure 3. The latter would have a positive effect on N supply to crops or vegetation.

The increased microbial and root activity in the soil would entail higher CO2 partial pressure in soil air and CO2 activity in soil water, hence increased rates of plant nutrient release e.

Similarly, the mycorrhizal activity would lead to better phosphate uptake. These effects would be in synergy with better nutrient uptake by the more intensive root system due to higher atmospheric CO2 concentration.

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There is no a priori reason why the degree of synchrony between nutrient release and demand by crops or natural vegetation would be subject to major changes under high CO2 conditions. The greater microbial activity tends to increase the quantity of plant nutrients cycling through soil organisms.

The increased production of root material at similar temperatures tends to raise soil organic matter content, which also entails the temporary immobilization and cycling of greater quantities of plant nutrients in the soil.

In all experimental situations, whether chamber-type or free-air enrichment, CO2 increases are rapid or sudden, often to double ambient concentration, sometimes higher. The consequently rapid increases in soil organic matter dynamics and soil micro-organisms may cause temporary competition for plant nutrients.

These temporary effects have on occasion been reported as negative factors affecting plant response to elevated CO2 However, increased organic matter dynamics and microbial activity in soils are positive for the soil-plant system when CO2 concentrations rise gradually over decades, as currently and in the recent past.

Future experiments could be set up to compensate for the temporary effects caused by the suddenness of the CO2 increase, for example by artificially higher soil organic matter contents estimated to be near equilibrium with each stepwise higher CO2 concentration, in a range between and ppm.Carbon emissions from warming soils could trigger disastrous feedback loop of exactly how warming will affect natural systems.

of the global soil carbon .

Global warming and how it will affect soil carbon

Carbon dioxide (CO 2) is the primary greenhouse gas emitted through human , CO 2 accounted for about % of all U.S.

greenhouse gas emissions from human activities. Carbon dioxide is naturally present in the atmosphere as part of the Earth's carbon cycle (the natural circulation of carbon among the atmosphere, oceans, soil, plants, and animals). NBC News/Wall Street Journal Poll conducted by Hart Research Associates (D) and Public Opinion Strategies (R).June , N=1, adults nationwide.

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Global warming and how it will affect soil carbon

Since the slowdown in surface warming over the last 15 years has been a popular topic recently, I thought I would show results for the lower tropospheric temperature (LT) compared to climate models calculated over the same atmospheric layers the satellites sense.

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Impact of Global Warming on Soil Organic Carbon - ScienceDirect