Is there concrete evidence that the greenhouse effect is changing our climate? This week we travel to Africa, Asia and North America to find out if the long predicated change is already having an impact on society and the economy.

Fish stocks plummet as temperatures rise

The North Pacific is one of the richest seas in the world, providing almost half of the fish and shellfish caught in the United States - with salmon accounting for 95% of the surface fish found in these waters.

But the times of plenty are over.

Scientists working for the Canadian department of Fisheries believe that there's a link between the decline in salmon stocks and a sharp rise in sea temperature - which has increased by 0.6 - 0.7 oc since the turn of the century. In addition, freshwater from melting glaciers is flooding the ocean's surface, diluting its salinity and upsetting the flow of nutrients from the deep ocean to the surface where fish feed.

Scientists believe that the resulting drop in food is the cause behind recent crashes in fish stocks - which could spell the end to commercial salmon fishing in the Pacific.

Forests stripped bare

Alaska's Spruce Pine forests are under attack - from a beetle. Warmer temperatures have brought the Spruce Beetle north into areas recently pest-free. The beetle, no longer limited by colder temperatures, now completes its life cycle three times faster than in cooler years. In some areas, more than 90% of Alaska's 1.2 million hectares of spruce forest is dead.

Vanishing glaciers

The state of Montana is home to one of the largest areas of undisturbed wilderness in the United States and the most southerly glaciers to be found on the continent.

But over the last 150 years almost three quarters of Montana's glaciers, and one half of the world's glaciers, have melted away as global temperatures have risen. And that's bad news for the low-lying islands facing a watery end as sea levels rise. What's more, scientists are beginning to understand how the world's oceans drive our weather systems and warn that any changes in sea level or temperature will effect the world's climate.

Storm warning

On the barrier islands of Chesapeake Bay, Maryland, scientists have monitored a ten-fold increase in the rate of sea level rise over the last ten years. If these islands disappear under the waves the mainland can expect increased erosion - putting more than 3.1 trillion dollars of coastal real estate at risk.

Further south, in the state of Florida, increased intensity of storms and floods is exacerbating coastal erosion. During the recent Hurricane Irene - a relatively minor Force 1 storm - much of downtown Miami was under water. The loss to business and soaring insurance rates may have long term economic repercussions.

Life and death

In the developing world climate change comes at a greater cost. Here, it's literally a matter of life and death.

Poor, densely populated low lying countries such as Bangladesh are particularly susceptible to climate extremes. With no cash to build flood defences, more than 110 million Bangladeshis living in flood-prone areas are at risk. Just thirty one years ago, a large flood claimed the lives of more than one quarter of a million people.

But for low-lying island communities, like the Maldives in the Indian Ocean, there is an even greater threat - total annihilation from sea level rise.

Health risks

It's not just the environment that will suffer, climate change can affect our health too.

There is an increasing body of evidence that links a rise in asthma cases to the combination of higher temperatures and air pollution from increasing amounts of ground level ozone, better known as smog.

Smog is caused by the very same CO2 gasses that contribute to global warming and climate change, and is exacerbated by increasing temperature, leading to a vicious cycle of CO2 fueled heat and pollution.

Rising temperatures have also been linked to the spread of malaria into previously disease-free regions. For many nations across Africa malaria takes its toll all year round, killing up to a million people a year. But in the cooler highland regions it used to be a different story.

In 1998 severe epidemics struck across East Africa, attacking highland populations who had never been exposed to the disease and had no immunity. Now scientists are the spread of 'highland malaria' in other areas of the world. In recent years, epidemics have been observed in Pakistan, Peru and Madagascar.

All around the world, global warming and the resulting changes to our climate - caused by pollution of the atmosphere - is making an ever greater impact. Next week we look at some solutions to rising greenhouse gas emissions. Wind farms, wave power and harnessing the massive potential of the suns energy.