A recent (Oct. 18) Denver Post article proclaimed ‘The World is on a path to add 57 superhot days a year’. This scenario- based on a climate study cited - assumes countries fulfill their promises (from the 2015 Paris Agreement) to curb CO2 emissions so that by the year 2100 the planet warms by only 2.6 C (4.7 F) above pre-industrial times. In that case “57 superhot days would be added to what the Earth gets now”.
This according to the computer simulations released by the climate
scientists belonging to The World Weather Attribution (WWA) and U.S. – based Climate
Central. (The AP report noting the study is yet to be peer-reviewed "but uses established techniques for climate attribution".). As the Post account from the AP also noted (quoting the study authors):
“Superhot days are defined for each location as days that are warmer than comparable dates between 1991 and 2020”
This makes sense given the past ten years, from 2015 to 2024, have been the hottest on record, with 2024 being the warmest year overall, according to scientific and weather organizations. Indeed, "since 2015 the world has added 11 superhot days on average."
The report also doesn't say exactly how many people will be adversely affected, but Climate Central VP for Science Kristina Dahl (a report co-author) warns:
"There will be pain and suffering because of climate change. But if you look at this difference - between 4C of warming and 2.6C of warming - that is encouraging"
She was referring to thc two scenarios, 2.6 C (4.7F) of warming and 4C (7.2 f) warming, the latter taken to be the path the world was on before the Paris Agreement. In other words, the study's authors have assumed our planet is and will remain on the less disastrous climate path. However, others disagree and we note - from the article:
"The 2015 Paris Agreement has made strides against climate change but its too little and too slow".
A take with which I concur. Further, lamebrained voters in the US of A put Trump back in power again even knowing he would set us back with his yen for fossil fuels. See e.g.
Given this, I firmly believe the worst IPCC scenario, not even referenced in the study, needs consideration.
This is the IPCC SSP5-8.5 scenario projecting an increase of 5.7 C (10.3 F) by the end of the century).
To find an estimate of the superhot days that would be added per year, say for the above SSP5-8.5 scenario, I tasked Chat GPT with the computations while using the basic data from the climate report. Below are the results found:
If global warming follows the high-emissions SSP5-8.5 pathway (about 5.7 °C by 2100 relative to pre-industrial), a simple extrapolation of the Climate Central / WWA results implies roughly ~180–195 extra “superhot” days per year on average worldwide by the end of the century — a best central estimate of about ≈188 extra superhot days per year (added to what we get today).
How I got that (step-by-step, with the report’s numbers)
The joint report gives two key points (all relative to today’s
climate):
- At 2.6
°C global warming → +57 extra hot
days / year (on average). Contentful
- At 4.0
°C global warming → +114 extra
hot days / year (on average). Contentful
You asked about SSP5-8.5 ≈ 5.7 °C (IPCC AR6 gives a
5–95% SSP5-8.5 range up to ~5.7 °C for 2081–2100). IPCC
Two reasonable ways to extrapolate from the report’s numbers:
Method A — linear extrapolation using the (2.6 → 57) and
(4.0 → 114) points
1. Difference
in extra hot days: 114 − 57 = 57 days.
2. Temperature
difference between those points: 4.0 − 2.6 = 1.4 °C.
3. Slope ≈
57 ÷ 1.4 = 40.7142857… extra hot days per °C.
4. From 4.0
°C up to 5.7 °C is +1.7 °C, so add 1.7 × 40.7142857 ≈ 69.21 days to 114 → ≈183
extra days.
Method B — use the report’s baseline “today”
(present ≈ 1.3 °C) and the 2.6 point
1. Present ≈
1.3 °C (report’s stated present warming). Contentful
2. Increase
from present to 2.6 °C = 2.6 − 1.3 = 1.3 °C, which corresponds to +57
days → slope ≈ 57 ÷ 1.3 = 43.8461538
days/°C.
3. Increase
from present to 5.7 °C = 5.7 − 1.3 = 4.4 °C, so 4.4 × 43.8461538 ≈ 192.92
extra days.
The two extrapolations give ≈183 and ≈193 extra
hot days; averaging (and allowing a sensible uncertainty band for nonlinearity
and model spread) yields a central estimate ≈188 extra hot days with a
plausible range of ~180–195 (I round conservatively to ~180–200
to reflect additional uncertainties).
Important caveats & context
- The
Climate Central / WWA report provides robust, multi-model averaged results
for 2.6 °C and 4.0 °C scenarios but does not report a
5.7 °C case explicitly — my answer is an extrapolation. The underlying
relationship is roughly linear between the two reported points, which is
why linear extrapolation is a reasonable first approximation, but it may not
capture non-linear physical or regional effects at very high warming. Contentful
- The
numbers are global averages across countries. Individual countries
(especially small island or tropical nations) can see much larger
increases (the report shows many places would receive well over 100 extra
hot days under 2.6 °C and far more at 4 °C). So local outcomes can be very
different from the global mean. Contentful
- “Superhot
days” here = days hotter than the 90th percentile of comparable dates in
1991–2020 (the report’s definition). The human impacts (health, labor,
mortality) scale with intensity, duration, vulnerability and adaptation —
so the raw added-days number understates complexity of real harms. Contentful
- SSP5-8.5
itself is a high-end emissions pathway; IPCC AR6 reports a wide model
range for that pathway (multi-model range up to about 5.7 °C by
2081–2100). Use of SSP5-8.5 implies very large additional warming and thus
very large increases in extreme heat days. IPCC
Bottom line
If the world follows a very high-emissions SSP5-8.5 path (≈5.7 °C by 2100), a conservative extrapolation of the Climate Central / WWA analysis points to on the order of ~180–200 extra superhot days per year on average globally (central estimate ≈ 188 extra days relative to today). That would turn large parts of the calendar into “superhot” conditions for many populations — a dramatic and dangerous shift.
The results here from the A.I. are stunning, but pretty well in line with what I already expected, from analyses I've done based on the net heating rate (due to CO2 concentration) of 2.7 W/ m2 per year.
See Also:
by Karl Grossman | July 31, 2025 - 5:00am | permalink
“Trump’s EPA to repeal core of greenhouse gas rules,” was the Reuters headline this week as Lee Zeldin, chosen by Donald Trump to be administrator of the U.S. Environmental Protection Agency, announced what Reuters said “will rescind the long-standing finding that greenhouse gas emissions endanger human health, as well as tailpipe emission standards for vehicles, removing the legal foundation of greenhouse gas regulations across industries.”
“Zeldin announced the agency’s plan to rescind the ‘endangerment finding’ at a truck factory in Indiana, alongside Energy Secretary Chris Wright, and called it the largest deregulatory action in U.S. history,” reported Reuters.
The move was anticipated.
And:
And:
And:
Smoke-filled Air, Ochre Skies Provide Preview Of Life At Cusp Of Runaway Greenhouse Effect
And:
New UN Report Issues "Code Red" For Humanity On Climate - Is It Hyperbole?
And:
Bjorn Lomberg - Climate Change Clown Has No Clue Concerning Adaptation To A Rapidly Warming World
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