More intense, more rain from 1°

I know everyone has been hit over the head about how these new breed of hurricanes are a result of Global Climate Change.  It is hard to imagine exactly how big these storms have gotten and why they are more powerful than they were before.  It all comes down to water one degree Celsius temperature increase.  What qualifies me to tell you, nothing really.  I have a university degree in Geography-Biology, which is the study of the 200m of the Earth where life exists, it involves an understanding of weather and the impact water has on the environment.  It involves an understanding of how life interacts with the environment.  It is enough to explain this subject in simple terms and to explain the simple processes that are at work.  Simple things can have a massive effect.

One degree!  How can one degree have such a significant effect?   it comes down to water.  Hurricanes are big storms that start close to the equator they are big enough that the Earth's spin has an effect on them.  It is not the spin that makes them strong or big though, it is the water.  Warm air and warm water.  The air is warm because it is sitting on the water and since the water is about a thousand times as dense, the water has a greater effect on the air than the other way. The water we are talking about is warm equatorial water, the warmest in the ocean.  It warms the air and the air picks up water that evaporates.  An interesting property of air is that the warmer it is, the greater the carrying capacity it has, meaning that it can hold more before it is saturated.  At lower temperatures the carrying capacity remains nearly constant, but at higher temperatures it increases rapidly with each incremental rise in temperature.  So the warmer the air, the more water it can hold.  

What does that matter.  Water is lighter than air.  Liquid water is denser than gaseous air, but water vapor is much lighter than air.  One mol of water weighs 18g one mol of oxygen weighs 32g, nitrogen is 28g, so you can see at air holding water is much lighter than dry air.  This means that wet air rises.  The wetter the air the faster it rises.  Rising air cools.  As air cools its carrying capacity for water drops and the water precipitates out as clouds.  Another thing happens when air rises, it reduces the air pressure on the surface of the Earth.  Wet rapidly rising air reduces the air pressure more than dry air.  This creates a low pressure zone.  Air from regions of greater pressure rush towards areas of lower pressure and this is called wind.  So wet air rises and creates clouds and a lower air pressure at the surface and thus wind.

As the hurricane forms e low pressure becomes greater and greater.  The air from increasingly greater distances gets drawn into the center to replace the air rising.  The air is spinning, because the air closer to the equator is moving faster than the air further away, because the Earth's rotation.  On a sphere, the the equator has a further distance to travel in the same time so its speed is greater.  So the air spins and just as a figure skater spinning slowly with her arms out, as she brings her arms in she speeds up, so to when the winds reach the center of the storm they speed up.  So this creates the spiral shape and the wind speeds at the center.  The center is a huge vortex the winds heading straight up and around leaving the very center calm.  That is a hurricane simply put.  So what does 1°C do to change that?

One degree increases the carrying capacity of air a lot.  The air is that much lighter than it would be without the extra heat.  When the air cools, that much more water is turned into clouds.  Warmer oceans create larger and more powerful storms, but not necessarily more stronger storms in terms of wind speed.  Hurricanes are rated in terms of wind speed at the eye of the storm.  Bigger storms have bigger eyes so they might have smaller wind speeds than if they had a more compact eye.  But the destructiveness of a storm can't just be measured in terms of wind speed, because the swath of destruction in a bigger storm is so much more wide and the amount of rainfall is so much greater.  And the eye could also have more windspeed too.  Hurricane Irma, was the most powerful hurricane in terms of windspeed and in terms sheer size, it is a monster.  As climate change increases, you can expect to see more Hurricanes, Cyclones and Typhoons, but they will be larger and more intense too, dropping more rain than ever before.