It is impossible to say what the weather will be like in 100 years! Quite apart from the difficulty in making predictions, it all depends on where you are in the world. Regardless of whether man made global warming is a reality, climate shifts have been occurring since the dawn of time and since the beginning of the 20th century there has been a general warming trend; however, even if we consider that this trend might continue through the 21st century, scientists do not entirely understand the consequences of global warming and it may be that some areas actually become colder and wetter rather than hotter and drier.
The last 2000 years has seen at least three distinct climate shifts. Warming during the middle-ages resulted in the Medieval Warm Period; cooling during the subsequent centuries resulting in the Little Ice Age; warming during the 19th and 20th centuries has given rise to concerns of man-made global warming. Arguments in the scientific community have centred not around the reality of climate change but whether or not man has had an influence on it.
Standard predictions are that the climate will be around 1-2.5 degrees hotter in 100 years. This may not sound like a lot but it could have major impacts on a number of weather systems. For example, the hurricane season is likely to be longer and hurricanes potentially more violent. There is already some evidence that tropical cyclones have been on the increase in the North Atlantic over the last 40 years and that trend would be set to continue. This is because hurricanes require a certain temperature level in order to form, and higher temperatures would give them longer to form and potentially make them more intense.
Changes in temperature are also likely to lead to changes in rain patterns. In tropical areas, the rainy season may last for longer. In temperate areas it may be shorter. However, there is a lot of doubt over this largely because there are a number of feedback factors that have to be taken into account. More heat potentially means more evaporation; but increased cloud cover may serve to cool some areas. Wind patterns could also be altered, meaning that existing weather systems reliant on prevailing winds may not exist in 100 years time.
The ocean is another potential influence on climate. Ocean currents transfer heat like conveyor belts across the planet, yet changes in temperature and melting ice caps may disrupt existing currents. There has been much concern in the UK, for example, that melting ice could cause the North Atlantic drift to change and thus create colder weather rather than warmer.
Predicting the weather in 100 years is a virtually impossible task; significant warming of the planet may lead to a number of changing weather systems that could have catastrophic effects in some areas, but the full extent of those changes cannot be known because of the sheer complexity of the global weather system.
