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Tonight I'm presenting the weather for Look North from the White Rose Awards - the annual event celebrating the best of Yorkshire's tourism industry. The industry has had a great year. A combination of recession, a weak pound and the early promise of a barbeque summer (!) meant more people stayed at home.

In fact Yorkshire tourism should get a huge boost in years to come if are correct.

Based on the most optimistic low emissions scenario, average summer temperatures in Scarborough by 2050 will be around 23C and summers will be 10% drier. Looking at the high emissions scenario, summer temperatures by 2080 could be as high as 26C - similar to those in Barcelona in June. The Yorkshire tourist industry would be transformed.

But the climate change message has been a difficult sell here in Yorkshire over the last few years. July, in Bradford, was the wettest since 1920. In fact it's only the fourth time since records began in the middle 1700s that we have had three consecutive Julys with more than 100mm of rain - 2007, 2008 and 2009 were all very wet.

The good news is that we have never before had four very wet Julys in a row. Also, we came very close to having another sequence of wet Julys in 1956, 1957 and 1958. And what followed in 1959 was one of the driest summers of the last century, with stand pipes in the streets! Some food for thought before you throw in the towel on the great British summer and decide to head abroad next year

And talking of wet summers, an interesting snippet I found out in a meeting with weather boffins last year. I was complaining that our viewers just weren't buying this drier and warmer summer story that climate models were telling us about. On the contrary I said, August 2004 was the wettest in Sheffield since 1922; and the summers of 2007 and 2008 were poor (and now 2009). How can we expect the viewers to accept what the climate models were saying, I said?

The answer surprised me. It turned out that looking at twenty model simulations from across the world, all said winters would be milder and wetter. All said summers would be warmer. But although a majority (13) said summers would be drier, a sizeable minority (7) said summers would get wetter. That's more than a third. That was news to me, and I'm sure news to a lot of you, too.

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Much in the news at the moment is the story about the dramatic loss of ice in the Arctic Ocean, and the likelihood that within the next twenty years it could be entirely free of ice in summer. The came from Professor Peter Wadhams at Cambridge University, who has been studying Arctic ice since the 1960s.

It's thought that loss of Arctic ice could itself lead to an acceleration in global warming. Firstly, ice is important in reflecting sunlight back into space, and so the less of it that we have, the more the sun's energy is absorbed into the sea, causing additional warming to occur in a well understood feedback loop.

More worryingly, research conducted by David McGuire of the U.S. Geological Survey show that the Arctic has been a carbon sink since the end of the last ice age which over time has accounted for between zero and 25 percent, or up to about 800 million metric tons, of the global carbon sink. On average, says McGuire, the Arctic accounts for 10-15 percent of the Earth's carbon sink. But the rapid rate of climate change in the Arctic could eliminate the sink and possibly make the Arctic a source of Carbon dioxide.

Although this year's Arctic ice has recovered in extent compared to the last couple of years, there is a clear trend towards less ice. Most scientists agree that man-made global warming has caused this loss of ice over the last few decades, and some would say it's happening even quicker than some climate models had predicted.

But in an unusual move, the Met Office sought to distance itself from Professor Wadhams in a issued on the same day.

In it they confirmed that Arctic ice decreased dramatically in 2007, but said this may have been wrongly attributed to global warming. 'Analysis of the 2007 summer sea-ice minimum has subsequently shown that this was due, in part, to unusual weather patterns. Arctic weather systems are highly variable year-on-year and the prevailing winds can enhance, or oppose, the southward flow of ice into the Atlantic', they said. Importantly they don't expect the Arctic to be ice free until the earliest 2060 - at least four decades later than Professor Wadhams' forecast, and conclude, 'The observed temporary recovery from the 2007 minimum in 2008 and 2009 indicates that the Arctic ice has not yet reached a tipping point, if such exists'.

But, on the other side of the world, something rather odd seems to be happening in Antarctica. The ice is actually increasing in extent, not decreasing.

So how does this tie in with warmer global temperatures? Well, as odd as it may seem, global warming may well be responsible, according to Jinlun Zhang, an oceanographer at the University of Washington.

He has pieced together a complex computer model that helps explain why Antarctic sea ice is growing even with signs that ocean and air temperatures are on the rise. The key is that warming temperatures can lead to more stratified ocean layers.

In the Southern Ocean, there's a layer of cold water near the surface and a layer of warmer water below. Normally, convection causes the two layers to mix and exchange water, a process that brings heat from the lower layers to the surface layer and ultimately helps keep sea ice expansion in check. But if the air gets warmer, the model indicates that the amount of rain and snowfall could increase, and surface waters could freshen. Since fresh water is less dense and less apt to mix with the heavier, saltier, and warmer water below, the layer at the ocean's surface could become more stratified and mix less. This, in turn, would reduce the amount of heat flowing upward, allowing surface ice to expand.

It's although thought that because of the hole in the ozone layer, weather conditions have changed. According to NASA Goddard scientist Josefino Comiso, the loss of ozone has caused lower atmospheric pressure over the Amundsen Sea. This causes colder, stormier and faster winds over the waters around Antarctica, especially in the Ross Sea, where ice growth is most rapid. The winds create open water near the coast that promotes sea ice production.

Water-logged sea ice also may explain why sea ice in the Antarctic is increasing. This occurs when the weight of accumulated snow presses down on a slab of sea ice until it's nearly submerged. When that happens, waves cause ocean water to spill on top of the ice and into the snow, forming a layer that eventually freezes and becomes "snow ice."
So, global warming is not only thought responsible for the melting of Arctic ice over the last few decades, but the observed increase in the ice at Antarctica, too.

Other parts of the Antarctica continent do seem to be showing the more straight forward impacts of global warming. As in August, one of the largest glaciers in Antarctica is thinning four times faster than it was ten years ago.

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Thanks for all your comments. To answer some of the points raised directly:

1) Which was the hottest year?

From the Met Office clearly show 1998 as the warmest year on record. Temperatures have levelled out and fallen since then. In fact last year, as you can see, was much cooler than 1998.

Should we 'strip' 1998 of El Nino? I didn't think so for my article, because we have always have had El Ninos and La Ninas. Also - where would you stop? Would you get rid of PDOs and ADOs, too?

2) Did the models predict that temperatures would level off?

None of the climate models suggested that global temperatures would not rise any further for at least another 10 years, which is what we have observed. The Hadley Centre model does incorporate ocean cycles. But that doesn't alter the fact that the models did not predict this. So the question must be, will it/has it captured the negative PDO that some scientists say will last for the next 20 odd years - and if it hasn't, why hasn't it? I also know that the Met Office are currently conducting research into why temperatures have levelled off/fallen from their peak.

Mine is by no means the only recent contribution to the argument on the Ö÷²¥´óÐã site. Many other reports by a number of correspondents have been published. For example, , knowing how our climate and C02 emissions have changed in the past is just as important as predicting what it's going to do in the future.

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The title of this may be a surprise. So might the fact that the warmest year recorded globally was not last year, or 2007, but 1998. For the last decade we have not observed any increase in global temperatures. What's more, climate models did not forecast it even though man-made carbon dioxide, the gas thought to be responsible for warming our planet, has continued to rise. So what on earth is going on?

Climate change sceptics, who passionately and consistently argue that man's influence on our climate is overstated, say they saw it coming. They argue there are natural climate cycles over which we have no control which dictate how warm the planet is. But what is the evidence for this?

During the last few decades of the 20th century, our planet did warm quickly. Sceptics argue that the warming we observed was down to the energy from the sun increasing; 98% of the earth's warmth comes from the sun. But research two years ago seemed to rule out solar influences. Its approach was to look at solar output and cosmic ray intensity over the last 30-40 years, and compare them with changing global temperatures. The results were clear. "Warming in the last 20 to 40 years can't have been caused by solar activity," said Dr Piers Forster from Leeds University, a leading contributor to this year's (IPCC).

One solar scientist, however, Piers Corbyn, from the long range forecasters , disagrees. He claims that solar charged particles impact us far more than is currently accepted, so much so he says, that they are almost entirely responsible for what happens to global temperatures.

Then there are oceans; the earth's great heat stores. And according to research conducted by Professor Don Easterbrook from Western Washington University last November, the temperatures of the oceans and the planet are related. He says the oceans have a cycle in which they warm and cool cyclically. The most significant is called Pacific Decadal Oscillation (PDO). For much of the 1980s and 90s, it was in a positive cycle- ie warmer than average. Global temperatures were warm too. But in the last few years it's started to cool down. In the past such cycles have lasted for nearly 30 years.

So could global temperatures follow? The global cooling from 1945 to 1977 coincided with one of these cold Pacific cycles. Professor Easterbrook continues 'The PDO cool mode has replaced the warm mode in the Pacific Ocean, virtually assuring us of about 30 years of global cooling'

So what does it all mean? Climate change sceptics argue this is evidence they have been right all along. They say there are so many other natural causes for warming and cooling, that even if man is warming the planet, it's insignificant compared to nature.

But those scientists who are equally passionate about man's influence on global warming argue their science is solid. The Met Office's , responsible for future climate predictions, incorporates factors like solar variation and ocean cycles, along with man-made greenhouse gases, into its climate models. It says temperatures have never gone up in a straight line, and there will always be periods of slower warming, or even temporary cooling. What's crucial is the long-term trend in global temperatures. And that, according to the Met Office, is upward.

To confuse the issue even further, last month, another member of the IPCC, Dr Mojib Latif of the at Kiel University , said that we may indeed be in a period of cooling worldwide temperatures that could last another 10-20 years. But he makes it clear he has not become a sceptic; he believes that this cooling will be temporary, before the overwhelming force of man made global warming reasserts itself.

So what can we expect in the next few years? Both sides have very different forecasts. The Met Office says warming is set to resume quickly and strongly. Indeed, it predicts that from 2010 to 2015 at least half the years will be hotter than the current hottest year on record (1998). Sceptics say it's unlikely temperatures will reach the heights of 1998 until 2030 at the earliest; indeed it's possible that because of ocean and solar cycles a period of global cooling is more likely.

One thing's for sure. The debate about what's causing global warming is far from over. Some would say it's hotting up.

A also appears in the section of the Ö÷²¥´óÐã News website.

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