Global Warming Has Now Passed The 1.5C 'Catastrophic' Threshold . . . . . And It's Making Cold Weather Worse!

This bright spark is an IPCC expert reviewer apparently.

He seems to think that just because the mean global temperature anomaly for the cherry-picked last 12 months has exceeded 1.5C, this means that we have passed the threshold for ‘dangerous’, nay catastrophic global warming agreed at the Paris climate summit as the limit which all nations would do their best to avoid going beyond by cutting emissions of greenhouse gases. He’s wrong. The 1.5C threshold refers to a long term average, ideally measured over a period of 20 years, not a measurement made over some randon 12 month period, as I pointed out here:

Dr Dunstone concluded: “It’s important to recognise that a temporary exceedance of 1.5 °C won’t mean a breach of the Paris Agreement. But the first year above 1.5 °C would certainly be a milestone in climate history.”

The Paris Agreement is widely accepted to refer to a long-term average of 1.5 °C, rather than an individual year.

To smooth temperature wiggles in model projections of future climate, the latest IPCC assessment report, AR6, defined the 1.5 °C mark and other global warming levels (GWLs) in terms of projected 20-year averages relative to the average for 1850–1900. The year of exceedance of a GWL is the midpoint of the 20-year period at that level. By this definition, 1.5 °C of warming would be confirmed once the observed temperature rise has reached that level, on average, over a 20-year period — in other words, a decade after crossing the 1.5 °C level

How can an IPCC expert reviewer not be aware of the definition of the Paris 1.5C threshold according to the latest IPCC AR6 report? He’s on X spreading this misinformation in support of climate alarmism and the abandonment of life-saving, poverty-reducing hydrocarbons. Where are the fact checkers calling him out for misleading his 33,400 followers? No ‘community note’ attached to that post either.

But it seems anything goes in climate alarmist clown world now.

h/t Doug Brodie. This was posted at the Conversation on March 4th:

The author claims that sudden stratospheric warmings (often resulting in severe cold snaps in winter and early spring) may be becoming more frequent . . . . . . because of global warming.

One less obvious consequence of global warming is also getting growing attention from scientists: a potential increase in the intensity and frequency of winter cold snaps in the northern hemisphere.

Weather phenomena like the Beast from the East in winter 2018, the cold spell of Arctic air that reached as far South as Texas in February 2021, or the storm that left Madrid and Athens unusually covered in snow for days in early 2021 are becoming more common.

Some of the mechanisms that lead to their occurrence are strengthened by global warming. Key climate mechanisms, like exchanges of energy and air masses between different altitude ranges in the atmosphere, are evolving in ways expected to cause an increase in both the intensity and duration of cold snaps. These link to the behaviour of a region in the high atmosphere called the stratosphere.

Some of these cold snaps are linked to disruptions in a seasonal atmospheric phenomenon called the stratospheric polar vortex (SPV).

In the northern hemisphere, this vortex consists of masses of cold air centred over the north pole, surrounded by a jet of very strong westerly winds between 15-50km above ground. These spinning winds act as a wall and keep cold air confined to the Arctic region, stopping it from travelling to lower latitudes.

Something that can disrupt the vortex is a sudden stratospheric warming (SSW), when the stratosphere experiences an abrupt increase in temperature due to energy and momentum being transferred from lower to higher altitudes.

When a major SSW occurs, the wall of strong winds around the polar stratosphere can break, allowing cold air to escape the polar vortex and travel down to lower atmospheric altitudes and lower latitudes. When that air approaches the Earth’s surface, significant cold spells can occur.

Even when SSWs are not strong enough to break the vortex, they can weaken it. This can cause polar air circulation patterns to meander further south into lower latitudes, reaching populated areas of North America and Eurasia, instead of staying nearer the north pole. Those areas can then experience temperatures tens of degrees lower than their winter average.

Under climate change, the transfer of energy from the lowest layers of the Earth’s atmosphere to the higher stratospheric layer is changing and seems to be disrupting the polar vortex to a greater degree. A study has shown that the strength and duration of SSWs in the stratosphere have increased over the last 40 years. This increase is also expected to result in stronger winter cold snaps at surface levels.

By sheer coincidence, a very rare ‘once in 250 year triple SSW has just happened, which promises to bring very cold easterlies to the UK:

A Sudden Stratospheric Warning (SSW) event usually strikes every two extended winters.

But this year the UK could see an ‘extremely rare’ trio of them.

Professor Adam Scaife, head of long-range forecasting at the Met Office, said: ‘Although we have not seen it before, we recently documented the chances of an unprecedented three SSW events happening in one winter.

‘Our research work, using multiple computer simulations, showed that this could occur about once in every 250 winters.’

The chance of cold and dry weather increases and 70% of SSW occurrences are linked to cold snaps.

Just for a change, the Met Office does not mention climate change in relation to this rare event:

For the first time since records began in the mid 20^th century , this extended winter period (November to March) is the first in our observational records to see three Sudden Stratospheric Warming (SSW) events. Met Office research suggests the likelihood of having three SSW events in one winter period is just a one in 250-year chance, although it is more likely to happen during an El Niño winter, such as this winter.

The record of SSW events goes back to the 1950s with the introduction of radiosonde balloons which are used to take observations high in the stratosphere on a routine basis. Since then, there has been typically one SSW every two extended winters. However, there are occasional runs of years with no warming events at all e.g. in the 1990s. There are also winters with two warmings such as the winter of 2009/10.

Professor Adam Scaife, Head of Long-Range Forecasting at the Met Office, said: “Although we have not seen it before, we recently documented the chances of an unprecedented three SSW events happening in one winter. Our research work, using multiple computer simulations, showed that this could occur about once in every 250 winters.”

Professor Scaife added, “Although this is very rare, we also found that the chance of multiple SSW events is increased during El Niño and so the chance of multiple events this winter is raised.”

I haven’t looked at this closely yet but one thing leaps out at me. We’ve got an ‘unprecedented’ third sudden stratospheric warming. Stratospheric warmings, according to one of the studies cited by the author of the Conversation article above, are intimately connected with stratospheric ozone:

The stratospheric ozone layer accounts for 90 % of the total existing atmospheric ozone and plays fundamental roles for atmospheric processes and for life on Earth. Ozone in this atmospheric region provides a vital shield against harmful ultraviolet (UV) radiation, preventing the most energetic UV-C and UV-B wavelengths (wavelength bands below 300 nm) from reaching the Earth's surface. UV radiation is absorbed by ozone in the stratosphere via very exothermic reactions. Therefore ozone is the main player in shaping the vertical temperature profile in the stratosphere and has a fundamental role in the interactions between radiation and dynamics in this region, as well as in the exchange of air masses with the troposphere.

Well, what do you know? The Hunga Tonga volcanic eruption is expected to have very significant effects upon stratospheric ozone, the most significant of which are projected to occur . . . . . . right now!

The January 2022 eruption of the Hunga Tonga-Hunga Ha'apai underwater volcano injected a large amount of water vapor into the mid-stratosphere. This study uses model simulations to investigate the resulting stratospheric impacts out to 2031. Maximum radiatively-driven model temperature changes occur in the Southern Hemisphere (SH) subtropics in April–May 2022, with warming of ∼1 K in the lower stratosphere and cooling of 3 K in the mid-stratosphere. The radiative cooling combined with adiabatic cooling driven by the quasi-biennial oscillation meridional circulation explains the near-record cold anomaly observed in the SH subtropical mid-stratosphere. Projected ozone responses maximize in 2023–2024 as the water vapor plume is transported globally throughout the stratosphere and mesosphere. The excess H₂O increases the OH radical, causing a negative global ozone response (2%–10%) in the upper stratosphere and mesosphere due to increased odd hydrogen-ozone loss, and a small positive ozone response (0.5%–1%) in the mid-stratosphere due to interference of the NO_x catalytic loss cycle by the additional OH. In the lower stratosphere, the excess H₂O is projected to increase polar stratospheric clouds and springtime halogen-ozone loss, enhancing the Antarctic ozone hole by 25–30 DU in 2023. Arctic impact is small, with maximum additional ozone loss of 4–5 DU projected in spring 2024. These responses diminish after 2024 to be quite small by 2031, as the excess H₂O is removed from the stratosphere with a 2.5-year e-folding time. Given the year-to-year variability of the stratosphere, the magnitudes of these ozone responses may be below the threshold of detectability in observations.

I have no idea at this point whether the disruption in stratospheric ozone caused by the injection of water vapour high into the stratosphere by Hunga Tonga may affect the likelihood of SSWs, but it seems to me that it is worth investigating as an alternative to saying ‘it was global warming wot dunnit’ yet again.