Sometimes a simple tweet can convey a great deal.

Take the one below as an example.

It's from Years of Living Dangerously, which produces documentaries on climate change, which are broadcast on the National Geographic channel.

It explains why the severe flooding in Texas is linked to global warming.

https://twitter.com/YEARSofLIVING/status/902176734078017537

Here's the text:

"Hurricane Harvey is pounding Texas.

"While hurricanes are nothing new, this one is.

"A couple of days before it hit, Harvey was still a tropical storm.

"But the waters of the gulf are so hot it more than doubled in intensity in 38 hours.

"It's also larger and packing more rain than typical storms...

"The affected area could get as much as 10 months of rain in just a few days.

"There is a reason behind all of this: as the planet gets hotter, oceans and lakes evaporate more...which leads to more water vapour in the air...which makes for more intense rainfall and more flooding.

"Climate scientists have also discovered that more heat on the surface of the oceans gives more energy to storms...which means not only more Harveys but more category 4 and 5 hurricanes coming our way.

"In other words...climate change is making the world's wet areas wetter.

"And as we can see...that's not good.

"These are #climate facts. Share widely."

This message was retweeted by the United Nations climate secretariat along with this message: "Good explainer by @YEARSofLIVING of how #climatechange made #harvey as destructive as it is".

For a more detailed examination about how climate change disrupts hydrological cycles, I recommend a book called Storm Warning: Water and Climate Security in a Changing World.

Written by Alberta climate researcher Robert William Sandford, it delves into detail about why a warmer atmosphere can carry more water vapour.

He describes how "atmospheric rivers" of moist air can derive tremendous energy as a result of Clausius-Clapeyron relation, which is a mathematical formula showing that vapour pressure steadily increases as the temperature rises.

In other words, Sandford writes in the book, "the warmer the air, the more water atmospheric rivers can carry".

That was on display in southern Alberta when torrential rains flooded downtown Calgary and caused havoc in High River. 

According to the Earth System Research Laboratory website, atmospheric rivers are, on average, 400 to 600 kilometres wide.

"A strong AR transports an amount of water vapor roughly equivalent to 7.5–15 times the average flow of liquid water at the mouth of the Mississippi River," the website notes.

In the meantime, here's what the climate-justice group 350.org has said about "how climate change contributed to Harvey's enormous, unnatural impacts" [the rest of what's posted came from a 350.org email sent out today]:

• Rising sea levels. Oceans have risen by more than a foot since 1960 in the Texas Gulf Coast. That's one more foot of storm surge that washed into homes and communities when Harvey made landfall.
  
  
• A warmer ocean means more rain. The Gulf of Mexico was anywhere from 2 to 7 degrees hotter [Fahrenheit] than usual before Harvey—well above 80 degrees [Fahrenheit] in total. That means more water evaporated into the storm, and more rain dumped on people on shore.
  
  
• A warmer ocean also means stronger storms. Harvey rapidly intensified from a tropical storm to a category 4 hurricane with winds above 135 miles an hour in just 48 hours. A hotter planet and a hotter ocean make this rare rapid intensification event more likely.

Denying climate science makes you unprepared for climate disasters. Here's how Trump's climate denial, racism and callousness are creating a truly unnatural disaster:

• Deregulating Big Oil’s toxic pollution. An environmental justice organizer with TEJAS, Bryan Parras, has reported strong, burning chemical smells coming from the refineries and chemical plants in East Houston. The Trump administration is rolling back regulations on Big Oil's pollution, and wants to eliminate the EPA office of Environmental Justice. These are the rules meant to protect vulnerable communities on the fenceline of huge oil refineries like the ones under siege in Texas right now.
  
  
• Cutting off immigrant communities. The Immigrations and Customs Enforcement kept running deportation checkpoints in South Texas in the leadup to the storm, trapping undocumented immigrants looking for safety from Harvey’s destruction. ICE's aggressive policing in immigrant communities in Texas has created a culture of fear that kept many families from seeking shelter in government facilities.
  
  
• Building in the path of the storm. Just last week Trump signed an executive order instructing the federal government to ignore climate change when constructing new infrastructure projects. That means he will be putting more Americans in the path of flooding like what we're seeing now in Texas.

Rains and flooding from Harvey are expected to continue for days to come. All of our thoughts and prayers are with the communities facing this storm right now. Many people will be rebuilding for years to come.