Tim Osborn
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timosbornclim.bsky.social
Tim Osborn
@timosbornclim.bsky.social
2.4K followers 480 following 270 posts
Climate variability and change | Professor of Climate Science & Director of Climatic Research Unit | UEA | Views expressed here are my own, not UEA's
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timosbornclim.bsky.social
HadCRUT5 global temperature dataset now updated to Sep 2025.

As usual, data can be downloaded from CRU/UEA website: crudata.uea.ac.uk/cru/data/tem...
And from Met Office/hadobs website: www.metoffice.gov.uk/hadobs/hadcr...

@climateuea.bsky.social @colinmorice.bsky.social
November 3, 2025 at 1:25 PM
timosbornclim.bsky.social
Climate stripes by longitude? Here's mine from 2004.
Estimates temperature changes from 1400-1960 over the mid to high latitudes of the Northern Hemisphere as a function of longitude covering North America, Europe and Russia. From work by Tim Osborn and colleagues in 2004, based on records of tree-ring maximum latewood density.
October 1, 2025 at 4:18 PM
timosbornclim.bsky.social
For regular monthly updates to CRUTEM (and hence to HadCRUT) we rely on monthly data provided by National Met Services via the WMO's CLIMAT system. Unusually, the USA data didn't yet make it into the CLIMAT data feed for Mar-Jun 2025. Note the USA-sized gap in the non-infilled version of HadCRUT:
September 22, 2025 at 9:51 PM
timosbornclim.bsky.social
Thanks! If you zoom in on the PDF version you can see how I drew the different levels of shading 👇
September 22, 2025 at 6:13 PM
timosbornclim.bsky.social
And some visualisations are available here:
crudata.uea.ac.uk/~timo/diag/t...
including 12-month running means of global land+marine (HadCRUT) and global land (CRUTEM) temperature anomalies
September 22, 2025 at 5:10 PM
timosbornclim.bsky.social
The update to Chinese station data makes a notable difference to the global land temperature data by making data for recent years more consistent with the historical data in the CRUTEM station database (which for China uses the mean of min & max temperature to represent the daily mean temperature)
September 22, 2025 at 5:10 PM
timosbornclim.bsky.social
After a brief (ahem) hiatus, the HadCRUT5 global temperature dataset has now been updated to June 2025 by @metoffice.gov.uk @climateuea.bsky.social and @ncas-uk.bsky.social
1850-2025 time series of global mean temperature anomaly from the HadCRUT5 dataset.
September 22, 2025 at 5:10 PM
timosbornclim.bsky.social
There’s still time to visit “A Field Hospital for Eco-Anxiety”, open till 28 Sep. It’s an installation at National Trust’s Dunham Massey, put together by “Not here to be liked” including input from UEA / CRU PhD student Erik Hartin.
@nationaltrust.org.uk @climateuea.bsky.social @ueaenv.bsky.social
September 11, 2025 at 4:00 PM
timosbornclim.bsky.social
John has a knack for finding the heart of the issue and expressing it in understandable terms.
Screenshot from diagrammonkey blog which says: "A recent paper on sea level change concludes that “approximately 95% of the suitable locations show no statistically significant acceleration of the rate of sea level rise. The investigation suggests that local, non-climatic phenomena are a plausible cause of the accelerated sea level rise observed at the remaining 5% of the suitable locations.” Having read the abstract, one can guess – more or less – what the problem is as it’s straight out of the sceptic playbook. 1. Take a global indicator with a clear signal 2. Break it down into as many local estimates as possible, maximising the noise to signal ratio. 3. Test each local change independently using a statistical significance test that is predisposed to accept the null (no change/no accelerations or whatever) and does not account for the possibility of a common signal. 4. Aggregate the results of the individual tests back up to the global scale (again ignoring any possible common signal) and express disbelief that anyone thought there was something there. It’s a way to avoid seeing the forest by a very careful study of all the individual trees."
September 11, 2025 at 1:31 PM
timosbornclim.bsky.social
UAH *does* agree that 2024 was the hottest year on record. Here's is the excerpt on tropospheric temperature (co-author John Christy from the UAH team). Perhaps your eye is being drawn to the slightly lower temperatures so far in 2025?
Transcript: 5. TROPOSPHERIC TEMPERATURE —S. Po-Chedley, J. R. Christy, C.-Z. Zou, C. Mears, and L. Haimberger Record-high global lower tropospheric temperature (LTT) values in the second half of 2023 persisted through boreal summer in 2024 (Fig. 2.9), producing a 2024 global-mean LTT that was 0.84°C (0.77°C–0.92°C depending on dataset) above the 1991–2020 climatological mean (Fig. 2.10). All nine tropospheric temperature datasets considered here (Table 2.3) ranked 2024 as the warmest year for global LTT, making 2023 the second-warmest year in most datasets.
August 15, 2025 at 10:35 AM
timosbornclim.bsky.social
To conclude: climate warming poses a serious threat to coral reefs (as highlighted in IPCC AR6 WG2, text here). Record-breaking one-year declines are alarming and a central part of how the impact plays out, but longer-term records provide essential context and shouldn’t be omitted.
Excerpt from IPCC Sixth Assessment Report, Working Group 2, Chapter 3 Executive summary. Text reads as follows: Climate impacts on ocean and coastal ecosystems will be exacerbated by increases in intensity, reoccurrence and duration of marine heatwaves (high confidence), in some cases, leading to species extirpation, habitat collapse or surpassing ecological tipping points (very high confidence). Some habitat forming coastal ecosystems including many coral reefs, kelp forests and seagrass meadows, will undergo irreversible phase shifts due to marine heatwaves with global warming levels >1.5°C and are at high risk this century even in <1.5°C scenarios that include periods of temperature overshoot beyond 1.5°C (high confidence). Under SSP1-2.6, coral reefs are at risk of widespread decline, loss of structural integrity and transitioning to net erosion by mid-century due to increasing intensity and frequency of marine heatwaves (very high confidence). Due to these impacts, the rate of sea level rise is very likely to exceed that of reef growth by 2050, absent adaptation. Other coastal ecosystems, including kelp forests, mangroves and seagrasses, are vulnerable to phase shifts towards alternate states as marine heatwaves intensify (high confidence). Loss of kelp forests are expected to be greatest at the low-latitude warm edge of species’ ranges (high confidence). {3.4.2.1, 3.4.2.3, 3.4.2.5, 3.4.4}
August 15, 2025 at 10:13 AM
timosbornclim.bsky.social
Southern GBR: 31% one-year decline: “which drove regional coral cover [now at 26.9%] below the long-term average of 29.3%”
1986 to 2025 time series of hard coral cover for the Southern Great Barrier Reef
August 15, 2025 at 10:13 AM
timosbornclim.bsky.social
Central GBR: 14% one-year decline: “however, it [hard cover cover at 28.6%] is still above the long-term average of 19.8%”
1986 to 2025 time series of hard coral cover for the Central Great Barrier Reef
August 15, 2025 at 10:13 AM
timosbornclim.bsky.social
Northern GBR: 25% one-year decline. “Despite this, coral cover [at 30%] remains above the long-term average of 26.6%.”
1986 to 2025 time series of hard coral cover for the Northern Great Barrier Reef
August 15, 2025 at 10:13 AM
timosbornclim.bsky.social
The "Jones" Gibraltar-Iceland NAO index now updated to June 2025. Data and viz here: crudata.uea.ac.uk/cru/data/nao/ @climateuea.bsky.social @ueaenv.bsky.social
Timeseries of winter-average NAO index
August 14, 2025 at 9:55 AM
timosbornclim.bsky.social
Delighted to announce that Ben Santer is now an Honorary Professor @ueaenv.bsky.social & the Climatic Research Unit (CRU).

Ben is returning to his "academic home": he did his PhD in CRU before his stellar career developing "fingerprint" methods to identify human & natural effects on climate.
Photo of Ben Santer
July 21, 2025 at 4:19 PM
timosbornclim.bsky.social
As always, @micefearboggis.bsky.social ‘s footnotes are worth reading diagrammonkey.wordpress.com/2025/05/04/n...
May 4, 2025 at 8:09 PM
timosbornclim.bsky.social
The dry spring is showing up in low riverflows in the north of England, and parts of south and east England too.

My animation of the EA's weekly summaries from www.gov.uk/government/p...
May 2, 2025 at 3:40 PM
timosbornclim.bsky.social
Norfolk-style dual carriageway
April 27, 2025 at 3:02 PM
timosbornclim.bsky.social
UEA campus enjoying some sunshine
March 26, 2025 at 12:23 PM
timosbornclim.bsky.social
On Saturday, IPCC @ipcc.bsky.social agreed the chapter outlines for AR7 WGI. Do follow @enb.iisd.org to keep track of what happens at IPCC meetings, they provide useful and detailed reports enb.iisd.org/intergovernm...
Outcome: On Saturday, WGI agreed to the revised chapter outlines for its contribution to AR7, as set out in IPCC-LXII/Doc. 11. The report will include the following chapters: Chapter 1: Framing, methods and knowledge sources; Chapter 2: Large-scale changes in the climate system and their causes; Chapter 3: Changes in regional climate and extremes, and their causes; Chapter 4: Advances in process understanding of Earth system changes; Chapter 5: Scenarios and projected future global temperatures; Chapter 6: Global projections of Earth system responses across time scales; Chapter 7: Projections of regional climate and extremes; Chapter 8: Abrupt changes, low-likelihood high impact events and critical thresholds, including tipping points, in the Earth system; Chapter 9: Earth system responses under pathways towards temperature stabilization, including overshoot pathways; and Chapter 10: Climate information and services.
March 5, 2025 at 10:43 AM
timosbornclim.bsky.social
Do you want to work on improving some of the most widely used global climate datasets?

We are offering a 34-month research / climate data science post to further develop CRU TS and CRUTEM @climateuea.bsky.social @ncas-uk.bsky.social
vacancies.uea.ac.uk/vacancies/14...
Cover page of the candidate brochure for a Senior Research Associate / Climate Data Scientist post at UEA
February 27, 2025 at 9:25 PM
timosbornclim.bsky.social
Where has it warmed the most and the least?

Observed warming has not been uniform and matches well the pattern that climate models predict

1. Warming has been greatest over the northern polar regions

2. Warming is generally greater over land than over the oceans
A map showing the pattern of long-term warming estimated from the HadCRUT5 global temperature dataset
January 10, 2025 at 4:19 PM
timosbornclim.bsky.social
Now that all groups have released their 2024 global temperature data, here is a comparison of their timeseries and their 2024 values
Graph showing timeseries of global temperature change from the pre-industrial level to 2024 from 6 different datasets, plus a panel comparing their 2024 values. Four are slightly above 1.5C, two are slightly below 1.5C.
January 10, 2025 at 4:07 PM
timosbornclim.bsky.social
In 2024, all four domains (NH land, NH ocean, SH land, SH ocean) had their warmest annual temperatures on record.

(Based on the CRUTEM and HadSST datasets that go into HadCRUT)
January 10, 2025 at 3:47 PM