Global warming will hit us not only in the atmosphere but also in soil underneath, warns new Canadian research.Researchers at Toronto University here have found that global warming will change the molecular structure of organic matter in soil, thus altering its natural decomposition process and affecting fertility as well as releasing more carbon dioxide into the atmosphere.

The release of more carbon dioxide will set in motion a self-perpetuating process - more carbon dioxide will speed up global warming. In turn, speeded-up global warming will lead to more release of carbon dioxide into the atmosphere and so on.

'Soil contains more than twice the amount of carbon than does the atmosphere, yet, until now, scientists haven't examined this significant carbon pool closely,' said a university statement quoting study leader Myrna Simpson.

'Through our research, we've sought to determine what soils are made up of at the molecular level and whether this composition will change in a warmer world,' she said.

According to the researchers, it is soil organic matter which makes dirt fertile and support plant life.Organic matter retains water in the soil and prevents erosion. Natural processes of decomposition of soil organic matter provide plants and microbes with the energy source and water they need to grow, they said.

Carbon is released into the atmosphere as a by-product of this process, the researchers added.Since global warming is expected to speed up the decomposition of soil organic matter, it will lead to an increase in the amount of carbon dioxide released into the atmosphere.

'From the perspective of agriculture, we can't afford to lose carbon from the soil because it will change soil fertility and enhance erosion,' said Simpson.'Alternatively, consider all the carbon locked up in permafrost in the Arctic. We also need to understand what will happen to the stored carbon when microbes become more active under warmer temperatures,' she said.

As soil is difficult to analyse, not much has been known about its molecular composition till now. But Simpson and her team used the new nuclear magnetic resonance (NMR) facility at the university to study soil's molecular structure.

During their 14-month outdoor field experiment, the team used electrodes that warmed the test soil between three and six degrees through winter and summer seasons and then analysed the molecular composition of soil samples.

From their analysis, they came to the conclusion that global warming actually changes the molecular structure of organic matter in soil.