The @IPCC_CH report is out, so let's talk about #drought. There are major advances in the report on this. In the last report (8 years ago) scientists weren't sure whether some of the bad droughts we were seeing were caused by humans. Things have changed. 1/
First, what is a #drought? It's complicated! You need low rainfall, but things that "remove" water from land (wind, temperature, evaporation) are also important. In Chapter 8 you'll find a diagram with all these factors. We tried to make it simple, but 🤣 2/ Diagram of drought drivers, with climatic factors on top, wa
Where has human influence made drought worse so far? Two hot spots are western North America and the Mediterranean. These places are labeled in the SPM with brown hexagons and double dots (more confidence in human influence) 3/ Areas of the world where humans have contributed to increase
What is interesting about these places is that it is not low amounts of rain that has been causing bad droughts. It's high temperatures (a consequence of rising greenhouse gases) leading to so-called "hot droughts" 4/
"Hot drought" happens because when the atmosphere is warmer, it is also thirster. A warm atmosphere evaporates more water out of soils, making droughts worse. So for the same reduction in rainfall, you get a more severe drought 5/ Infographic explaining "hot drought". In a normal
An example: the 2012-2014 drought in California. An analysis of tree ring data by @thirstygecko & @locallyabsent demonstrated that this drought was not unusual in terms of low rain but once you considered soil moisture, it was amongst the worst in 800 years! 6/
Let's shift to the future. What can we expect under higher emissions? This map from FAQ 8.3 highlights places where projections suggest droughts will get worse. 7/ World map with locations that are expected to experience wor
Unsurprisingly, many semi-arid places (western NA, Med, Chile, SW Australia, S Africa) are expected to get drier but some wet places are on this map as well, like the Caribbean and the Amazon. 8/
Figure 8.19 shows in more detail how the projected changes scale with emissions scenario. In this plot, Vapor Pressure Deficit (VPD) is used as a metric for how "thirsty" the atmosphere is. Soil moisture reflects the balance of precipitation, evaporation, and transpiration. 9/ Global maps of projected changes in drought metrics, from th
Bottom line: More emissions = thirstier atmosphere = more severe droughts. If we cut emissions sooner rather than later we can avoid the worse-case scenarios. /fin #ClimateReport #IPCC

• • •

Missing some Tweet in this thread? You can try to force a refresh
 

Keep Current with Jessica Tierney

Jessica Tierney Profile picture

Stay in touch and get notified when new unrolls are available from this author!

Read all threads

This Thread may be Removed Anytime!

PDF

Twitter may remove this content at anytime! Save it as PDF for later use!

Try unrolling a thread yourself!

how to unroll video
  1. Follow @ThreadReaderApp to mention us!

  2. From a Twitter thread mention us with a keyword "unroll"
@threadreaderapp unroll

Practice here first or read more on our help page!

More from @leafwax

9 Aug
This has been the news recently, so let's go over what the @IPCC_CH has to say about whether the Gulf Stream will shut down in the coming decades. Short answer: it's not likely to happen. Long answer: keep reading 1/ washingtonpost.com/climate-enviro…
Chapter 9 has an *awesome* FAQ (shout out to @baylorfk ) about this which I encourage you to read. It starts by clarifying what exactly the Gulf Stream is, which is important 2/ Diagram of the Gulf Stream and the Atlantic Meridional Overt
The Gulf Stream is a warm current that flows off of the eastern United States. At these latitudes it is part of the subtropical gyre, which is driven by winds. These winds (trades, westerlies) are going to blow no matter what, so there will always be a Gulf Stream 3/
Read 12 tweets
8 Aug
The @IPCC_CH report will be released in the early AM tonight. I helped author it, and tomorrow I'll tweet about some of the findings re: #drought which was one of the things I worked on. In the meantime, it's worthwhile knowing a few things about the process 1/
IPCC authors like myself do not get paid! We volunteer. It's a three year commitment and it becomes a deep part of your life. Why do we do it? Because we care about making sure the world knows about what has happened and what will happen if we don't cut emissions. 2/
The text in the IPCC report went through two rounds of public peer review, during which time anyone (I mean anyone!) could read the draft and submit comments. The authors have to respond to *every* comment (there are thousands). #accountability 3/
Read 13 tweets
21 Feb
So, do you all know who the lead author is of that 42,000-yr climate event Science paper? It's this guy. nature.com/articles/d4158…
This totally fits with the energy of the paper, which makes unsupported claims about both the genetics and paleoclimate data. Here's a great thread about problems with the former
For the latter, all you have to do is have a quick look at some of the best climate records we have - ice cores (high latitude) and speleothems (tropics), to see that *nothing happens* at 42,000 years.
Read 6 tweets
12 Feb
It's #FigureFriday, so let's chat about my favorite subject: color palettes 🎨 for climate science visualization! (1/12)
First, why is it important? Put simply: a beautiful figure can communicate your results more effectively than text. It can make a figure more understandable to a public audience. So it is worth it to put care into your figure design. (2/12)
First, if you're plotting up climate model data, especially anomalies, I highly recommend Cynthia Brewer's palettes on ColorBrewer. BrBG is my go-to for precip anomalies, and RdBu is a natural for temperature. (3/12) colorbrewer2.org/#type=divergin…
Read 12 tweets
5 Nov 20
The timing could be better 🥺 but our major review paper on past climates has just dropped in @ScienceMagazine. In this review, we argue that past climate climates are key to predicting the future 🗝️ science.sciencemag.org/content/370/65…
Our future climate trajectory is still unknown, but it's going to be toasty: comparable to many of the warm climates of the past 100 million years.
Earth history tells us what the climate system does under higher carbon dioxide. Not only should we study it more, but we should use paleoclimates in model evaluation. For example, to test whether the high ECS in some of the new climate models is legit. 🧐
Read 7 tweets
26 Aug 20
Our paper on Last Glacial Maximum (LGM) cooling and climate sensitivity is out today in @nature! This represents four years of work, so it feels really good to see it released. Here's a short thread on what it means... nature.com/articles/s4158…
First we compile almost 2,000 geological measurements of sea-surface temperature, which believe me took some time! Then, we ran new simulations of the LGM with the @NCAR_Science CESM model, and used data assimilation to combine the info. This gives us global maps of temperature! Image
This new analysis suggests that globally, the LGM was 6C (11F) colder than preindustrial times. This is a little colder some previous estimates but agrees well w/ others Image
Read 6 tweets

Did Thread Reader help you today?

Support us! We are indie developers!


This site is made by just two indie developers on a laptop doing marketing, support and development! Read more about the story.

Become a Premium Member ($3/month or $30/year) and get exclusive features!

Become Premium

Too expensive? Make a small donation by buying us coffee ($5) or help with server cost ($10)

Donate via Paypal Become our Patreon

Thank you for your support!

Follow Us on Twitter!

:(