2X increase in the most extreme hurrucanes!
Yesterday’s post connecting Melissa’s extra intensity to warmer ocean temperatures ruffled some feathers. Some complained that “one storm” doesn’t prove climate change.
That’s true.
So I dug deeper.
Looking at every Cat 4 & 5 in the Atlantic since 1980 (reliable records/ good data gathering) I broke the record into 2 equal parts.
1980-2002 and 2003-2025
What I found surprised even me. The most recent period has more than double the number of most intense hurricanes in the Atlantic!!
That’s not coincidence. Humans have become a force of nature. Through greenhouse warming and changes in aerosols (pollution) the oceans have warmed dramatically.
For instance, the water under #Melissa was about 4 degrees F hotter than it would have been ~100 years ago.
That’s huge! That extra heat powers a higher horse power engine with heavier wind & rain.
Is there a natural oscillation (AMO)component too? Perhaps, but IMO it’s tenuous.
In post analysis it’s very possible Melissa will be upgraded to the strongest Atlantic hurricane ever given lots of unprecedented data collected just before landfall.
With that said, personally I post this info simply because I find it interesting the degree to which we have changed the trajectory of our climate.
But - to be clear - I don’t ask that you do anything about it. The way you use this info and take action - or not take action - is not my business. To each his/ her own.
Personally I want to be sure I’m not denying reality by ignoring the symptoms. And I want to be sure I’m communicating the science to the public, as my position requires.
What you do with the info is your business. H/T to @BhatiaKieran his post yesterday on Rapid Intensification

The North Pacific heatwave these past few months has been astonishing. Take a look at the bottom of this image. It’s “accumulated heat stress” from NOAA’s Coral Reef Watch program. Basically the whole north basin registers Alert Level 5, dark purple. The dark purple also happens to correspond with areas that have been 5-8C (9 to 14 F) above normal at some point in the past few months.
(Luckily there is little coral impacted as this alert level
5 is for surface water north of the coral zone. I’m no biologist but I imagine it has a big impact on ocean life)
Now - I hope you are sitting - because take a look at this next graphic for September from @ZLabe 🧵 1/ Top right is how far “off the charts” September 2025 sea surface temps are in this area of the North Pacific. >1.6C or ~3F above normal on average over this huge area.
I’d say even more alarming than the actual anomaly is the trend since 2010. In 15 years the anomaly jumped more than 2F!
Much of this is likely due to the unmasking of global warming from the decrease in aerosol pollution. This allows for more ocean heating from more direct sun getting through and reduction in clouds due to feedbacks. 2/

I don't think you can understate just how impressive this heat dome is. It covers 2/3 of the nation in which 80% of the country's population over the 7 day heatwave period will hit 90+ for a high temperature (~260 million people)
The peak intensity of the heat dome was record breaking for the SE US in late July. It peaked at 3.7 standard deviations, based on statistics from the past climate records we have, which means this heat dome is rare, if not virtually impossible, in our former climate of the 1900s. But human-caused climate change now makes these extreme heat domes much more likely.
From the climate scientists at World Weather Attribution:
“Every heatwave in the world is now made stronger and more likely to happen because of human-caused climate change.”
A note: Its not the strongest heat dome I’ve seen and ground temperatures, although very hot, are not breaking many all-time records. The surface temps are not quite commensurate with the power of the heat dome aloft mainly due to the elevated low-level moisture from the Gulf.
Yes, as a climate specialist, I am very aware that climate change is not the only factor as to why it’s hot. I’m aware there is alot of asphalt making it hotter in cities. I’m aware it was record hot in the 1930s. I know the climate has always changed and the Earth goes through hot/ cold cycles. I know we are near sun spot maximum. I know all this, and more, because I have a Master’s degree in climate and I study this Every day. Thank you for coming to my Ted Talk.
A few sources for this post are in the thread below… #heatwave #heatdome @WFLA Here’s the map showing that 280 million are impacted by 90 degrees plus.

What are the odds this July’s Mediterranean heat is natural?
About 1 in a billion!
It's the most extreme Mediterannean heatwave on record. Peak anomalies +8C (+14F) now off France/ Italy with absolute peak temps near 31C/88F.
Those are isolated, but how deviant are the overall Med SST's from the norm? Around 6 deviations (sigma) or a roughly a 1-in-a-billion chance. So, basically, it's NOT possible in a natural climate.
BUT heat waves like this are not caused solely by climate change. So let's dig deeper with a thread... 1/ First, let's establish the sigma. In June the standard deviation from the 20th century mean was about 5-6 in the Western Med and not quite as deviant in the eastern Med. This deviation built larger as the month unfolded and is peaking for now. 2/

Alert: #Milton may threaten #TampaBay midweek.
I’m not an alarmist, it takes a lot to get my attention. This has it. If Milton landfalls at or just north of Tampa Bay as a cat 2-3 hurricane, it means up to double #Helene storm surge. And extensive, long term power outages 1/ While the exact track/ intensity is to early to know, a hurricane traveling across the Gulf from the west/ WSW is a worst case scenario for, if it hits at or north of the mouth of Tampa Bay. The 1921 borderline Category 3 which hit Tarpon Springs pushed 10-12 ft of surge in 2/

New: 2 rapid attribution studies on the impact of climate change on Hurricane #Helene have just been released. The results are very significant, yet unsurprising.
Warmer air, warmer water = much heavier rainfall rates. First study: ~50% increase in rain in parts of NC/ GA!! 🧵 First from @MichaelFWehner, who is one of the World’s experts on the connection between climate warming and Tropical cyclones.
“…our best
estimate is that climate change caused over 50% more rainfall during Hurricane Helene in some
parts of Georgia and the Carolinas.” 2/

As you may suspect both the dewpoint in FL (surface moisture) and more importantly the precipitable water (total column moisture) in June have been trending up.
For every 1F increase in temperature, the column can hold 4% more moisture. We have warmed ~3F since pre-industrial 1/

https://twitter.com/WeatherProf/status/1801387121812586959

Wow now have the capacity for ~12% more moisture. Thus the capacity to fuel more frequent/intense rain. In some cases more moisture means more instability, thus stronger storms & rain rates. Per @MWehner2005 CC spiked Harvey by up to 38%, w/ CC's share of the damage $13B 2/

25,000 years ago this is how Florida’s coastline looked. Sea level was 427 ft lower with all the water locked up in miles-thick ice at the peak of the last ice age. If you lived in Tampa you’d needed to walk 100 miles W to go to the beach. Follow along on this very educational🧵

https://twitter.com/weatherprof/status/1798849597353439386

This is what it looked like at the last glacial maximum. Ice spread all the way down to NYC and Chicago. If you go to Central Park in NYC you can see the edge of where they ended, there are huge boulders there. These ice ages have occurred every ~100K years recently. Here’s why…

This image is astonishing for both the message it communicates and for its sci comm value. Incredible work by team @CopernicusEU
It shows global ocean temps for each year since 1940. The alarming, yet brilliant part is the pink shading which highlights the 2023-2024 jump 1/

https://twitter.com/weatherprof/status/1798486436494086371

From 2023-2024 all areas in deep red were record warm. A huge area.
In May 2024 that record hot area was ~25%, so 1/4 of our planet. Huge amount. 2/

Putting aside the Gulf Loop Current, speaking more generally about warming water, in a perfect environment (moist, low shear) for every 3F of sea sfc warming, a strong hurricane’s wind speeds can inc. 20%. So a 150 mph storm, can grow to 180mph storm, and damage pot. ⬆️ 67% 1/

https://twitter.com/weatherprof/status/1795587321548730780

Sea sfc temps across the Gulf & Carib are ~3F warmer than a few decades ago. That’s one reason we should care about a warming world.
The example I use is based on an already strong hurricane in a nurturing environment, but it can happen. Source for calc: michaelmann.net/sites/default/…

“The climate always changes”… that’s true. Over tens of thousands of years Earth’s tilt changes a bit and so does Earth’s orbit around the sun… sometimes closer to a circle, sometimes an ellipse. This changes the amount of sunlight Earth receives and thus Earth’s avg temp 🧵 1/

https://twitter.com/weatherprof/status/1783629515756859753

As a result of orbital changes, every ~100,000 years the Earth sees an ice age. In between - where we are now - are warm periods called interglacials. Notice the difference is only 10 degrees F!
Those changes are natural and generally gradual.
But a century ago that changed 2/

The science behind this weekend’s 265 mph jet stream! A trans Atlantic flight reached an astonishing 835 mph. So Lets talk about meteorology, how climate change factors in and not breaking the sound barrier… 🧵 1/ The reason: two jets converge into 1 over the US and a sharp contrast of frigid vs warm air enhance the wind.
The result: a 265 mph upper level jet helps boost a Newark to Lisbon flight to peak speed of 835 mph reaching Lisbon in 5:44…. About an hour faster than normal! 2/

A testament to how extreme & overwhelming the climate is this summer is, this Record “Shattering” heat dome has been barely covered by the national media. It’s largest US heat dome in recent memory and in a large part of the nation’s middle the most intense, by a long shot. 1/ The highest heights (altitude to reach the 500 mb pressure level) on record in Omaha, Springfield & Topeka were around 6000 meters. Heights reached 6020 to 6030 meters. That’s a huge anomaly. This is a measure of heat dome strength… hotter air expands and raises the dome. 2/

There’s so many extreme weather and climate stories this weekend, with #Hilary’s impact, many are flying under the radar. This summer we are 1.5C above preindustrial and here’s just a small glimpse of my timeline. I’ve excluded a bunch of events. 1/ 2/

I've posted a lot lately about how hot the Gulf of Mexico waters is. The question I always get is, how may this impact hurricanes? I'll answer that and show you just how "off the charts" the Gulf sea surface heat is in this thread, with a couple of stellar visuals 1/ First the Q of hurricanes. This shows the "maximum" potential wind a hurricane can achieve IF conditions are perfect (light wind shear, minimal dry air, no land interaction). The scale maxes out in the Gulf at 170kts (195 mph). BUT perfection is almost never achieved. And this 2/

Wow. Even for the bath tub waters in the Gulf of Mexico this is impressive. Clearwater Beach this afternoon 93.4F. Buoy 100 miles west of Tampa Bay 91.5, Old Port Tampa 95, Port Manatee 93. These #'s are about 3-4F above normal. Gulf is at record hot levels which helps... 1/ ...explain, with winds from the west, why the low temperature this morning was only 84 (daily record). Dewpoints along the coast have been running 80-82... During the early morning that means a heat index of 95 and with 95+ degree highs, heat index numbers are 110-115+ 2/

Think July was hot in the desert SW? Aug says hold my beer. A monster heat dome likely by next weekend - the most intense yet this summer. Magenta indicates where all-time record heights are forecast. This on top of PHX so far beating its hottest month on record by almost 4F!! 1/ So far in July PHX avg temp is 102.9
Old record 98.9 in 2020. To beat your hottest month’s temp by ~4 degrees is remarkable. Enter August… This next heat dome is forecast to be around 4 sigma. These heat “ridges” measure the column heat by how high the 500mb pressure sfc is 2/

Another day of astonishing heat in the shallow waters of Florida Bay & the Keys!! 99.1 F on the edge of the Everglades. Close to a global record. This water is murky/dark so it absorbs more radiation. But even if it's elevated, it shows just how intense this marine heatwave is 1/ Here's the proof. And notice how a nearby site is 97.5. But it's worth mentioning there was a paper recently showing that these shallow water instruments are possibly registering readings up to a 1 degree elevated. 2/

This summer we’ve seen a very amplified pattern in the jet. This graphic helps explain how meteorologists forecast heatwaves. We look for upper level ridges (termed heat domes when they come with anomalous heat). Right now we have a series of heat ridges and also cool troughs 1/

https://twitter.com/weatherprof/status/1681087826425782278

That means in certain places who are trapped under cool troughs in the upper levels we also have pockets of cool air at the surface. So in the US some areas were actually quite cool in June. 2/

With record hot ocean I’ve had a lot of Q’s about the impact on hurricanes. Water temp is only one factor. I’d argue shear, or lack of, is more important. This shows the “potential” strength of hurricanes right now based only on heat/energy from the ocean. Dark blue=H5=Cat 5 🧵 The dark blue shading near South Florida and the Gulf of Mexico is appearing weeks early because water temps are at record levels, far above record levels in near South Florida. So if somehow a storm found it’s way here with low shear it could achieve this potential BUT 2/

Lots of talk about the very warm Gulf of Mexico, specifically focused on South Florida. Sea “surface” temps in the Florida Keys are 92-95 degrees. That’s boiling for them! More typically it would be in the upper 80s. This map shows departures from normal of ~5 degrees F 🧵 1/ The bleaching alert status is Alert level 1. The scale goes to 2. I bring this up because coral are extremely sensitive to slight changes (just a few degrees) in water temp. They have a narrow thermal range. The alarming part is that less than 5% of Keys coral cover is left. 2/