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Climate Models Underestimate Warming: Observed 1.1ºC Rise in Just 20 Years

Introduction

Meteorological data recorded over the last 20 years by sensors at the Roque de los Muchachos Observatory indicate an average temperature rise of 1.1ºC. Analysis led by UAB researchers reveals this increase is more than twice what climate models had forecast for this region and even exceeds predictions for the coming two decades.

Study Overview

Researchers Involved

Researchers from Universitat Autònoma de Barcelona's Department of Physics conducted an extensive study on the climate at the Roque de los Muchachos Observatory on La Palma, a key northern hemisphere astronomical site. Their findings are published in the Monthly Notices of the Royal Astronomical Society.

Observatory Details

At a site 200 meters below the main ridge that holds major telescopes like the Gran Telescopio Canarias, the MAGIC Telescopes, constructed to detect high-energy gamma rays with contributions from UAB researchers, are also accompanied by the Cherenkov Telescope Array Observatory (CTAO) construction for the northern hemisphere.

Data Collection Methodology

Data Collection and Analysis

Researchers Markus Gaug and Lluís Font from UAB meticulously analyzed a rare, extensive meteorological dataset spanning 20 years, gathered by instruments on the MAGIC telescope control building. The weather station documented:

• Temperature
• Relative Humidity
• Atmospheric Pressure
• Wind Parameters

Data was recorded at two-second intervals throughout.

Sensor Reliability

Markus Gaug explains that "The station was originally installed to assist with telescope operations, not to conduct professional local weather assessments or analyze climate change effects on the measured parameters." However, he notes, "The relatively low-cost sensors have proven advantageous, as they required replacement and recalibration approximately every two years. This regular maintenance has enhanced data reliability by minimizing long-term sensor drift, a subtle but challenging issue."

Historical Context of Temperature Variations

Established Weather Stations

Although AEMET only established a professional weather station at Roque de los Muchachos in 2022, data from 36 other AEMET stations across Tenerife have enabled long-term studies on temperature variation in the Canary Islands.

Temperature Trends

• Some studies report a decadal temperature rise of 0.3ºC between 1970 and 2010.
• Later studies with data up to 2014 observed a lower rate of 0.25ºC per decade, whereas models predict an increase of 0.3ºC to 0.5ºC per decade from 2015 to 2050.

Findings from UAB Study

Temperature Rise Analysis

Through the analysis of data collected since 2004 by the MAGIC telescopes, UAB physicists applied advanced statistical techniques to accurately gauge local climate trends. The results reveal a temperature rise of 1.1ºC over the past 20 years, or 0.55ºC per decade—more than double the rate predicted by current climate models for this region and higher than expectations for the coming decades.

Additional Climate Variability Observed

• Diurnal Temperature Range: Results further reveal a 0.13ºC per decade increase in diurnal temperature range, representing the difference between daily high and low temperatures.
• Seasonal Temperature Variability: A 0.29ºC per decade rise in seasonal temperature variability.
• Relative Humidity: One of the most noteworthy observations is the 4% per decade rise in average daily relative humidity.

This increase has also been documented in studies at the Mauna Kea observatory in Hawaii, diverging from the declining humidity trends reported at other continental observatories.

Explanation for Observed Trends

One potential explanation offered by the researchers for the observed differences between the island and continental observatories is the rise in seawater evaporation linked to global warming.

In response to concerns raised by the scientific community regarding climate change's effects on data integrity and observatory viability, scientists closely monitored climate variations at key locations, including the Roque de los Muchachos observatories.

Implications for Astronomy and Climate Monitoring

Stability of the Canary Islands Atmosphere

The subtropical atmosphere of the Canary Islands is particularly prized for astronomical observation due to its exceptional stability year-round. Positioned above a thermal inversion layer, the MAGIC telescopes benefit from low pressure and outstanding observing conditions characterized by dry and pristine air.

Weather Impact on Operations

Fortunately, the UAB study revealed no significant alterations in rainfall frequency or, more critically, in the incidence of severe storms. One key finding from the researchers was that temperature variations have consistently remained below half a degree per minute across all measurements, a criterion that aligns with the operational requirements for the forthcoming Cherenkov Telescope Array Observatory (CTAO).

Conclusion

Future Outlook

"At present, linear models do not indicate any evidence suggesting that the changes observed in meteorological conditions might hinder the operation of the telescopes or lead to increased periods of inactivity due to severe weather in the years ahead. Nonetheless, these results highlight the concerning speed of global warming," explains Lluis Font.

The Need for Continued Research

"Additionally, we recognize that beyond a certain temperature rise, the linear relationship within the climate system can break down, pushing us toward 'tapping points' where climate behavior can change dramatically," explains Markus Gaug.

Source

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