The dog days of summer have new meaning. The heatwaves we're living through aren't weather anymore — they're a signal. And the signal correlates, directly and unforgivingly, with global warming, which correlates, directly and unforgivingly, with how slow humanity has been to bend the climate curve.
The numbers are not abstract. 2024 was the first calendar year to cross 1.5°C above pre-industrial levels, and 2023, 2024, and 2025 now stand as the three hottest years ever recorded — the first three-year stretch with an average above 1.5°C. On a single day in July 2024, 44% of the planet was under strong-to-extreme heat stress. And the increasing heat rate is steepening: the pace of warming has gone from roughly 0.2°C per decade to something closer to 0.3–0.4°C since around 2015. That's not a line. Or temperature is starting to turn into an up-sloping curve.
So here's where I land. We're here now. We need to keep trying as hard as we possibly can to solve the problem: keep bending the curve, keep pressing forward on the hard decarbonization work that flattens that curve back down, or at least slows its rate of acceleration.
But we also need to fill the other gap: the one where the heatstroke has already arrived and isn't waiting for our emissions math to work out. We need pain-killers, not vitamins, for the people and businesses who are going to feel this first and feel it hardest. Today, we see it most in the devastating effects of forest fires. Soon we will see it concretely everywhere; and a lot more than you would think at sea and on the coast.
So let me walk through a selection of the coastal and ocean businesses that are going to suffer from heat — and where I think the pain-killers get built.
Hotter water changes everything downstream
Fisheries. A few years ago I read The Unnatural History of the Sea by Callum Roberts. It tracks the centuries-long decline of global fisheries — a combination of relentless new fishing technology meeting a near-total lack of data and clarity. The result: a textbook tragedy of the commons–we watched a slow-motion eradication of fisheries that people had assumed were infinite.
Hot water is not going to help.
A much warmer ocean means species will have to migrate to survive; commercially important fish have already been shifting poleward at roughly 52 km per decade, and under a high-warming path global maximum catch potential is projected to fall 20–24% by the end of the century. Worse, warm water holds less oxygen, which exacerbates the ocean's low-oxygen zones. This is a genuinely scary concept where whole city-sized swaths of the water column become unlivable for fish because they can't breathe. The number of these "dead zones" has gone from around 45 before the 1960s to roughly 700 by 2011. It's basically a hazmat zone with a coastline. A fisherman or lobsterwoman doesn't need a climate model to understand that; they need the fish and lobster to be where they've always been, and increasingly they aren't.
Tourism. This one is less about whether the water is warm enough that people do or don't want to swim in it. I spent some of the summer in the Mediterranean-which is a lovely bathwater temperature. It's that warm surface water that becomes a breeding ground for all sorts of stuff that is fundamentally incompatible with humans. And because the heating doesn’t give a damn about where people go to the beach, it shows up in places that were never set up for it to coexist with human activity. Vibrio vulnificus, the flesh-eating bacterium, has been expanding its range up the US East Coast at roughly 48 km per year, with roughly one in five infections proving fatal. Coastal algal blooms have grown more frequent and larger over the last two decades. Sargassum is on our doorsteps, and it isn’t exactly pleasant or normal for the average beachgoer. And the economics are not small: Florida's 2017–2019 red tide has been estimated to have cost coastal hotels, restaurants, and businesses around $2.7 billion in lost revenue. A beach town's entire business model assumes the water is an amenity. Warming quietly converts it into a liability that town has no playbook for.
Materials. Some things are engineered to operate — or to float, or to hold — in cold places, and as those places warm there will be a raft of small, adaptive, unglamorous changes to materials, coatings, and tolerances. It shows up everywhere. Examples we’re seeing with increasing frequency: cold-water hull coatings and antifouling designed for one biofouling regime now face warmer-water fouling organisms arriving earlier and staying longer. Lubricants, resins, seals, and buoyancy foams spec’d for cold operating ranges are drifting out of tolerance. There’s going to be a run on our built infrastructure, transport and recreation not standing up to the elements the same we are used to.
Operating conditions: a hotter world is just more expensive to run
Heatwaves and a permanently warmer atmosphere quietly raise the cost of running a whole category of businesses. Not with a single dramatic event, but with a thousand small taxes on operations.
Industries that rely on ambient temperature or cool operating water have a material adjustment to make. Anything that dumps heat into a river, a bay, or the air was designed around a temperature envelope that is now moving. We're seeing this show up in real time: this summer France was forced to cut more than 5 GW of nuclear capacity when river water ran too warm and too low to cool the reactors, and in June its exportable power surplus collapsed from 11–12 GW to under 3 GW. At one point jellyfish — thriving in the warmer water — clogged the intakes and shut reactors at France's largest nuclear plant. And it's not just power: cooling is becoming one of the defining operating costs of the digital economy, with one estimate putting climate-driven data-center operating costs at $81 billion a year by 2035, extreme heat driving the majority of it.
Labor. People are the operating cost nobody prices until they can’t work. By 2030 heat stress is projected to erase 2.2% of total global working hours — the equivalent of 80 million full-time jobs and about $2.4 trillion in lost output a year, per the International Labour Organization. Already, 2.4 billion workers — about 71% of the global workforce — are exposed to excessive heat. The people who work in conditions where ambient natural temperature was there to moderate–the docks, the decks, the farms, and the coastlines–are on the front line of that number. We’re seeing this show up in entrepreneurs focused on cooling wearables, tools for shift-scheduling, or new workforce training applications. I expect we’ll start to see a lot more of this once businesses and labor unions identify these problems as lasting, and not acute.
Aquaculture and mariculture. Farming — on land and in the water — runs on narrow temperature bands. Farmed Atlantic salmon grow best between about 13–16°C and lose appetite and growth above 18–20°C; sustained warm water has already produced brutal loss events, from ~2.6 million salmon dying in Newfoundland in 2015 to a warming-linked algal bloom that killed roughly 12% of Chile's national salmon production in 2016. Every degree compresses the margin for error in an industry that's supposed to be part of how we feed a warming planet.
The follow-on effects nobody's pricing yet
Finally, heat has second-order effects that aren't top of mind today but will be; the ones that don't show up in the first spreadsheet and then dominate the third.
- Insurance and capital flight from the coast: as heat compounds storm, flood, and health risk, coastal property and marine operators face rising premiums or outright non-renewal, and capital quietly reprices anything with a coastline.
- Cold chain and food safety: warmer ambient temperatures mean more refrigeration, more spoilage risk, and more pathogen exposure across seafood and coastal food systems.
- Infrastructure not built for this envelope: ports, cables, coastal power, and desalination intakes all engineered for a cooler baseline, now aging into conditions they were never designed for.
- Public health as a coastal cost center: I can see the headlines in a couple of years – PUBLIC OUTCRY AS BEACHES CLOSED. – but it may come to this. Vibriosis, algal toxins, and heat illness are turning into a recurring line item for coastal municipalities and the businesses that depend on them.
- Migration of people, not just fish: as the most-exposed coastlines become harder to live and work on, labor and populations move, and the economics of entire coastal regions shift underneath the businesses operating there.
Why I spend MY time here
I spend a lot of time focused on this because the physics don't lie. I also have been told by smart people that a good VC finds a trendline just before it turns exponential. The whole job is being early to a curve everyone else still reads as a line.
The heat index has already turned exponential. The question isn't whether the pain arrives at the coast, it's who's building the pain-killers when it does. At Propeller, we want to fund solutions bending the curve, but we also want to fill these gaps in pain-killers for the present.