Atmospheric events can be labelled as a hazard when people or infrastructures are at risk. However, sometimes an atmospheric event would not become a hazard in the first place, if it wasn’t for human developments interfering with natural processes. In ancient times, people didn’t have the technology we have today, and learned how to live with atmospheric events. The flooding of the river nile, was actually beneficial to the ancient Egyptions. However, these days urbanisation has caused floods to become extremely hazardous. For example, engineering developments to shorten the Mississippi River, may have been the main cause of the flooding in 1997, rather than the heavy rain. Other human actions can also turn a flood event into a hazard, such as roads, footpaths and roofs that don’t let water to infiltrate through them, increasing the amount and rate of run-off. Also some streams that have been filled in to make way for urban development, greatly increase the burden for the remaining streams to cope with flood waters. Bridges, jetties and other obstructions cause a build up of flood waters by slowing down river flow. Many rivers cannot cope with the increased flow of from a cities drainage system during times of heavy rainfall. Floods are not the only atmospheric event which humans influence. Droughts occur as a combined result of the climate and the activities of people who live in the region. The actions of people worsens the drought by felling trees for firewood and to build houses, and by poor farming which is causing desertification. This increase in desert serves to make the climate drier and so increases the drought risk. These examples show that human activities can influence the frequency and magnitude of an atmospheric event, turning it into a potential disaster.
The frequency, strength, and location of hazards such as storms, floods, droughts, heatwaves, cyclones, and wildfires are intimately connected to a longer period of global change in whether due to natural variations or human-induced changes. The use of resources such as fossil fuels like coal, oil and gas by humans, creates greenhouse gas emissions. These emissions collect in the atmosphere and trap in heat, causing the world to become warmer. Global warming effects climate zones on a global scale causing increased variability in the climate—greater swings of high and low temperature; larger cyclones; more tornadoes; drier and longer droughts; more and bigger floods.
Global warming could cause the Tropical Low Pressure belt to become more powerful and create more tropical cyclones. This is because cyclones draw their strength from the heated surface layers of the sea. The warmer the sea, and the deeper the heated layer, the more powerful the storm will be. These cyclones will occur further towards the poles, affecting countries that are not prepared for this sort of hazard. The subtropical high pressure cells may also move further pole wards which would cause the desert to move further south, causing desertification an increased drought in sub Saharan countries.
As average global temperatures are rising, so is the frequency and intensity of heat waves, causing more heat-related deaths. The warmer temperatures, decreased rainfall and increased evaporation caused by global warming, is increasing the occurance of droughts. These conditions are also increasing the risk of wildfires worldwide. Global warming is also causing an increase in El Nino weather patterns in the tropics. This problem poses a big threat to Australia, because the likelihood of an El Niño occurring is high in areas where drought is common. This will cause extreme droughts and bushfires to Australia.
Global warming is also causing the polar ice caps to melt. This is resulting in a rise in sea level, which may cause floods in some low-lying islands and coastal areas. Intensified weather conditions from global warming are causing severe storms in some parts of the world. This is causing more frequent and devistating flash floods.
Atmospheric hazards are not just natural phenomena. Human impact on the environment can influence the frequency, magnitude and location of these events. It can be the actions of humans that can turn an atmospheric event into a hazard, or human induced climate changes that intensify a hazard.
