La Nina, characterised by a drop from normal sea-surface temperatures across the eastern tropical Pacific, causes irregular climate patterns, including more intense downpours, which is what is happening in rainy season. Elsewhere, La Nina causes natural disasters, such as drought in the US Midwest or fiercer hurricanes in the Gulf of Mexico.

The name La Nina (Spanish for "the little girl"), was coined only in the mid-1980s, and the phenomenon has received a lot less attention from the scientific community and the general public than El Nino (the little boy), its better known counterpart. But after wreaking havoc around the world, La Nina can no longer be ignored.

According to climate-change experts, there have been only three La Ninas, compared to seven El Ninos, in the past 20 years.

In El Nino, the lowering of sea-surface temperatures in the eastern tropical Pacific causes the warm pool located in the central and western Pacific to expand to cover the tropics, resulting in prolonged drought, which was what happened in Thailand until a few years ago. But in La Nina, easterly trade winds strengthen the cold upwelling in the eastern tropical Pacific, causing sea-surface temperatures there to fall below normal levels. In Thailand, the effects of La Nina could be exacerbated by a rise in sea-surface temperatures in the Gulf of Thailand.

It is still not clear how big an impact the current La Nina will have on society and the environment. But last month's flash-floods and mudslides in the northern provinces that claimed 77 lives, affected almost 200,000 people and damaged 300,000 rai of farmland should be considered a wake-up call to the government and society at large.

Some climate-change experts warn that the North faces the possibility of more flash-floods and mudslides, Bangkok may experience historic flooding and the South is likely to experience huge storms.

How prepared is Thailand for the societal and environmental impacts of La Nina? Judging from the lack of a working natural disaster early-warning system, which resulted in the high casualties in the flash floods and mudslides in Uttaradit, Sukhothai and other northern provinces, Thailand still has far to go to protect itself from potentially disastrous natural phenomena.

Just a few days after the deadly mudslides struck Uttaradit on May 23, the Mineral Resources Department made the shocking statement that most of those who perished could have been saved if only local officials had followed existing precautionary measures for torrential rainfall and ordered the evacuation of communities located at the foot of mountains or in valleys. The department reported that all of the areas affected by mudslides and flash-floods in that province had previously been designated as areas prone to natural disaster. And local officials had apparently received instructions in the past in regard to following clear-cut early-warning procedures, including a contingency plan for evacuating residents from high-risk areas.

The safety precautions involved community leaders and local officials closely monitoring rainfall in areas prone to mudslides and flash-floods. An early warning must be issued and evacuation begun as soon as the rainfall exceeds 60 millimetres in a 24-hour period. Rainfall surpassing 100mm in 24 hours warrants community leaders and local officials to alert the district office to prepare for a rescue operation.

It became clear that these safety procedures were not followed. The Meteorological Department said up to 330mm of rain was recorded in the 24 hours preceding Uttaradit's mudslides and flash-floods.

Clearly there is a need for better public education to help people understand the risks associated with living in disaster-prone areas so that they can be expected to follow safety procedures consistently. More resources should also be made available to climate-change experts, meteorologists, civil defence planners and other relevant policy-makers to find out more about the potential impacts on society and the environment from fluctuating climatic conditions.