According to John Sweeney of the Irish Climate Analysis and Research Unit (Icarus) at NUI Maynooth, fish such as salmon and cod will be the first to succumb in warmer waters. "Fish are very sensitive to temperature changes . . . for example, with cod, their kidneys will fail if the temperature rises much more, " he said.

"Salmon are seriously struggling already. We also have some very rare Arctic species, such as the char. They live in the lakes of Wicklow and Donegal and they will come under a lot of stress from temperature change."

However, while we will lose some species to climate change, Sweeney said they will be replaced by fish attracted to warmer seas, such as tuna, sunfish, jellyfish and certain types of algae.

Already, there have been numerous sightings of these newcomers, including a shoal of warmwater anchovies off the coast of Donegal in 2002.

"It is not inconceivable that the great white shark will be attracted to this area in the next few decades also, " said Sweeney. "There's already a family of great whites living in the Mediterranean, so it's possible that they might appear here in the future."

The arrival of sunfish, in particular, is a significant indicator of climate change, according to the experts. "We have been seeing a phenomenal number of them this year, " said Tom Doyle, a marine biologist with the Coastal and Marine Resources Centre. Doyle has been given funding by the Irish Research Council for Science Engineering and Technology to monitor and track the movements of sunfish in Ireland.

"Historically, they've been here for a long time, but never in such abundance, " he said.

"We're seeing up to 20 in one day now, which is really phenomenal. And we can expect to start seeing more and more of them if the sea temperatures do continue to rise."

The sunfish, known in Germany as "the swimming head" is a highly unusual-looking creature. Growing to three metres long and weighing up to two tonnes, it is the largest bony fish in the world. "They don't have a backbone so they're basically all head, " said Doyle. "We're still trying to work out how it functions."

Despite their strange appearance, sunfish are not actually dangerous, although they are related to the puffer fish . . . a tropical poisonous fish eaten by the Japanese as a delicacy.

Joining them in Irish waters are an increasing number of leatherback sea turtles. "These turtles don't occur in waters with a temperature below 150C, and we are seeing more and more of them around Ireland, " said Doyle. "They used to arrive here in very low numbers, having travelled thousands of kilometres from the tropics, but now they are much more of a regular feature. We had 15-20 sightings of them this year alone."

Doyle said both the sunfish and the turtles are feeding on the jellyfish that have also started appearing in larger numbers around the coast.

"We don't know if it's due to climate change, but there has been an increase in the jellyfish population also, " he said. "For example, we have seen a lot of the Lion's Mane jellyfish, which is one of the most venomous in the water."

This particular species of jellyfish grows to a diameter of up to two metres and is vivid yellow, orange or sometimes red in colour. It pulsates just below the surface and has stinging threads of up to 30 metres in length that can cause a very unpleasant sting lasting for hours.

"They have been causing serious problems off the coast of Dublin, " said Doyle. "In the last couple of years, a number of beaches have had to be closed because of them."

MEANWHILE, according to the experts, climate change is also making Ireland a very attractive destination for a range of unwelcome insects and diseases, including mosquitos, hornets and outbreaks of malaria.

"Because of the absence of frost during the winter, more generations of insects are able to procreate per year, " said Icarus's John Sweeney.

"We will see more insects and an increase in insect-borne diseases, such as the Bluetongue disease that is carried by midges and affects livestock."

For humans, the increase in the mosquito population here will quite possibly lead to outbreaks of malaria, said Sweeney. Contrary to popular myth, a small number of mosquitos already live in Ireland but, as the weather gets milder, their number is expected to increase.

"Everyone has been noticing this autumn these long-legged creatures in their bedrooms and bathrooms, and I suspect these creatures are mosquitos, " said Sweeney. "Most mosquitos are not carrying a disease, but you will have a certain amount being brought in by travellers and some of these will be carrying malaria. With the milder winters, these disease-carrying mosquitos will survive and I would say it's not inconceivable that we'll get localised breakouts of malaria around Dublin Airport and in certain parts of Ireland."

The country is also quite likely to be invaded by very unwelcome immigrants such as hornets, according to Roy Anderson of Queens University Belfast. With extra warmth and thriving garden centres, Anderson foresees "a continuous and increasing accumulation of non-pestiferous but invasive alien invertebrates in Irish forests with unknown consequences".

Among these alien species are two new types of large and troublesome pine weevils that have already arrived in the northwest, and the great spruce bark beetle, said Anderson.

The experts have also already noted the effect that climate change is having on the bird population. According to Liam Lysaght of the National Biodiversity Data Centre, the warmer weather is having a significant impact on the Greenland white-fronted goose . . . one of the rarest geese in the world.

"One of the starkest changes we've seen is the migration patterns of these geese, " said Lysaght.

"They are now departing a month earlier than they were 30 years ago. On average, they're leaving one day earlier every year. Sixty percent of all the Greenland white-fronted geese live in Ireland, so it's a very significant change. We need proper scientific monitoring to keep track of their movements."

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UNITED NATIONS GLOBAL ENVIRONMENT OUTLOOK

Last week, the United Nations released its fourth Global Environment Outlook report, compiled by 390 experts from observations, studies and data garnered over two decades. The following are some of the latest stark facts on climate change:

Climate is changing faster than at any time in the past 500,000 years.

With more than six billion humans, earth's population is now so big that the amount of resources needed to sustain it exceed what is available.

Over 30% of amphibians, 23% of mammals and 12% of birds are now threatened.

Over the last two decades, the world population has increased by almost 34%, but the land available to each person is shrinking, from 19.5 acres in 1900 to five acres in 2005.

There is a rapid rise in "dead zones" where marine life can no longer be supported because of pollution.

There will be a global collapse of all species being fished by 2050 if fishing around the world continues at its current pace.

The earth has experienced five mass extinctions in 450 million years, the latest of which occurred 65 million years ago. A sixth major extinction . . . of our closest relatives, apes and monkeys . . . is underway this time caused by human behaviour.