unpredictable heat waves global map

Mysterious Heat-Wave Hotspots Emerge Worldwide, Leaving Scientists Puzzled

Record-Breaking Temperatures and the Rise of Extreme Heat Events

2023 holds the record as the Earth's hottest year, with an average temperature 2.12°F above the 20th-century norm. This exceeded the previous high set in 2016. Remarkably, the past decade has seen the top 10 warmest years ever recorded. With the hottest summer and single day in history, 2024 is poised to break new records.

The Emergence of Extreme Heat-Wave Hotspots

This may not come as a surprise to all, but amid the steady rise in average temperatures, a striking anomaly has emerged: certain regions are experiencing recurring heat waves so severe they surpass the predictive scope of current global warming models.

Mapping the Hotspots

Researchers in the Proceeding of the National Academy of Sciences have published the first global map pinpointing regions of recurrent extreme heat waves, seen across every continent except Antarctica as prominent, alarming hotspots. These heat waves have caused extensive loss of life, destroyed agriculture and forests, and triggered devastating wildfires.

The Role of Climate Models in Predicting Extreme Heat

Unprecedented Heat Wave Records

The study points out that the significant and surprising margins by which recent regional extremes have broken historical records have raised important questions about the effectiveness of climate models in predicting the connections between global temperature changes and regional climate vulnerabilities.

Lead author Kai Kornhuber, an adjunct scientist at Columbia Climate School's Lamont-Doherty Earth Observatory, explained, "These extreme trends arise from physical interactions we may not fully comprehend. These regions turn into temporary hothouses." Kornhuber is also a senior research scholar at the International Institute for Applied Systems Analysis in Austria.

Focusing on heat waves from the past 65 years, the study identifies regions where extreme heat is increasing far faster than more moderate temperatures. As a result, maximum temperatures are frequently shattered, with some exceeding previous records by remarkable, and at times surprising, amounts.

The 2021 Heat Wave in North America

For example, a nine-day heat wave that struck the U.S. Pacific Northwest and southwestern Canada in June 2021 shattered daily temperature records in some areas by as much as 30°C (54°F). This included Canada's highest-ever recorded temperature of 121.3°F in Lytton, British Columbia. Tragically, the town was destroyed by a wildfire the following day, Fueled by the drying effects fo the extreme heat. In Oregon and Washington, hundreds of fatalities occurred due to heatstroke and related health issues.

A Decade of Intense Heat

While some extreme heat waves have occurred as early as the 2000s or prior, the most significant heat events have predominantly taken place over the last five years. The hardest-hit regions include densely populated areas in central China, Japan, Korea, the Arabian Peninsula, eastern Australia, and various parts of Africa.

Hard-Hit Regions

Other affected regions include Canada's Northwest Territories and High Arctic islands, northern Greenland, the southern tip of South America, and scattered parts of Siberia. While areas of Texas and New Mexico are included, they are not among the most extreme locations.

Heat Waves in Northwestern Europe

According to the report, the strongest and most sustained signal comes from northwestern Europe, where successive heat waves resulted in around 60,000 deaths in 2022 and 47,000 in 2023.

Unique Vulnerabilities

These deaths occurred throughout Germany, France the United Kingdom, the Netherlands, and other countries.

In recent years, the hottest days of the year in this region have warmed at twice the rate of the average summer temperatures. The area is particularly vulnerable, partly because, unlike regions such as the United States, air conditioning is rare, as it was historically unnecessary. These heat waves have persisted, with new temperature records being set as recently as this September in Austria, France, Hungary, Slovenia, Norway, and Sweden.

Tail-Widening: The Statistical Trend

The researchers refer to the observed statistical trends as 'tail-widening,' describing the unusual rise in temperatures at the extreme upper end, which goes beyond what would be anticipated from a simple increase in average summer temperatures. However, this phenomenon is not universal; the study reveals that maximum temperatures in many other regions are actually lower than what models would predict.

Areas with Lower-Than-Expected Heat Increases

These regions include large parts of the north-central United States and south-central Canada, the interior of South America, much of Siberia, northern Africa, and northern Australia. While heat is rising in these areas as well, the extremes are increasing at a pace similar to or slower than what would be expected based on average temperature changes.

Potential Causes of Extreme Heat Events

The Role of the Jet Stream

Rising temperatures contribute to the increased likelihood of heat waves in many instances, yet the exact causes behind these extreme heat events remain unclear. A previous study in Europe and Russia, led by Kornhuber, attributed heat waves and droughts to disturbances in the jet stream, a fast-moving air current that circulates the northern hemisphere.

Historically confined by the frigid temperatures of the far north and the warmer air to the south, the jet stream typically follows a narrow path. However,the Arctic is warming significantly faster than most other regions of the world, which seems to be destabilizing the jet stream. This instability leads to the formation of Rossby waves, which pull hot air from the south and trap it in temperate areas that usually do not experience prolonged extreme heat.

This hypothesis is just one of several, and it does not appear to account for all the extreme events. A study of the deadly 2021 heat wave in the Pacific Northwest and southwestern Canada, led by Lamont-Doherty graduate student Samuel Bartusek (also a co-author of the current paper), found that multiple factors were at play. Some seemed related to long-term climate change, while others were more coincidental.

A third element was a series of smaller atmospheric waves that took heat from the Pacific Ocean and directed it eastward over land. Much like Europe, the region's relatively low use of air conditioning, due to its historically temperate climate, likely contributed to the high number of fatalities.

The heat wave was so severe that it could be classified as a 'black swan' event, one that defies prediction, according to Bartusek. However, he adds, there's a fine line between what is completely unpredictable, plausible, and foreseeable, making it difficult to categorize. 'I would label this more as a gray swan,' he said.

The Ongoing Impact of Heat Waves

Heat Wave Death Toll and Awareness

While the United States, with its resources, is better prepared than many nations, excessive heat continues to cause more deaths annually than all other weather-related events, including hurricanes, tornadoes, and floods. A recent study from August shows that the heat-related death rate has more than doubled since 1999, with 2,325 fatalities in 2023. This has led to suggestions that heat waves be named, akin to hurricanes, to rise awareness and encourage government action.

According to Kornhuber, these heat waves, due to their unparalleled intensity, are typically associated with severe health consequences and can wreak havoc on agriculture, vegetation, and infrastructure. "Our systems are not designed to withstand such extremes, and our ability to adapt may not be fast enough," he warned.

The study was co-authored by Richard Seager and Mingfang Ting from Lamont-Doherty Earth Observatory, along with H.J. Schellnhuber from the International Institute for Applied Systems Analysis.

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Middle East and North Africa to Face Alarming Temperature Surge, Experts Warn

Accelerated Climate Change Threatens the Rigion

A recent study highlights that the Middle East and North Africa, already among the hottest and driest regions globally, are experiencing accelerated climate change, likely reaching critical warming thresholds 20 to 30 years ahead of other areas. By the end of the century, regions of the Arabian Peninsula may face temperature increases of up to 9°C (16.2°F).

The region, already known for record-breaking summer heat, is nearing an average warming of 2°C (3.6°F) above pre-industrial levels. Further temperature increases could render certain areas uninhabitable without adaptive strategies.

Paris Agreement Goals Surpassed in the Region

"The Paris Agreement emphasizes limiting global warming to 1.5°C, with a maximum threshold of 2°C," explained Abdul Malik, climate scientist at King Abdullah University of Science and Technology and lead author of the study. "However, parts of the Middle East and North Africa have already surpassed these thresholds."

The research has been published in the journal JGR: Atmospheres.

Developing Models for a Fast-Warming Region

The Middle East and North Africa, characterized by vast desert ecosystems, have populations primarily concentrated along coastal areas. Previous climate models have varied in their predictions, often misestimating regional warming and leaving scientists with an incomplete understanding of its nuances.

High-Resolution Analysis Offers New Insights

This study utilized CMIP5 and CMIP6 models to conduct a high-resolution analysis (81² km or about 50 mi²) of the Middle East and North Africa, offering a more detailed understanding of regional warming.

While earlier research has established that the region warms significantly faster than others, Malik highlighted, "Our findings reveal that the warming rate is uneven across the region, ranging between 1.5 to 3.5 times the global average."

The accelerated warming rate suggests that the Middle East and North Africa could hit 3-4°C (5.4-7.2°F) of warming approximately 30 years before the global average, with inland areas of the Arabian Peninsula particularly affected.

Temperatures Rise in a Hot Region

The Middle East and North Africa are home to some of the planet's hottest areas, with researchers forecasting sustained rapid warming. The central Arabian Peninsula is already warming up to three times faster than the global average, matching the pace of Arctic warming.

Projected Temperature Increase by 2100

By 2100, the Arabian Peninsula may experience an average temperature increase of 2.6°C (4.7°F) under low emission scenarios, and up to 7.6°C (13.7°F) under high emission scenarios.

This is due to the inability of the dry deserts in the Middle East and North Africa to cool down efficiently through soil moisture evaporation, unlike their humid equatorial counterparts around the world.

Desert Regions Warm Faster Than Polar Areas

"Desert regions warm nearly as quickly as polar regions, but with significantly higher temperatures," said Georgiy Stenchikov, a retired climate scientist and co-author of the study. "As a result, the temperature threshold is reached much sooner than in the polar regions."

Regional Variations in Warming and Potential Mitigation

Due to coastal cooling effects, densely populated regions along the southern and western coasts of the Arabian Peninsula, such as Oman, are not warming as rapidly as inland areas and the eastern coast of the peninsula.

The warming rates very across seasons. The study identified summer hotspots in central Arabian Peninsula regions, including Riyadh Province, and in Algeria, while winter hotspots were found in Mauritania and Iran's Elburz Mountains.

The Role of Emissions Targets and Adaptation

If global emissions targets are met, the warming rate in the Middle East and North Africa could decrease by as much as 38%. In addition, cities may mitigate extreme heat through urban greening and architectural innovations.

"Adaptation will be essential, and the Middle East and North Africa could serve as testing grounds for these measures," Stenchikov explained. "Global warming is a worldwide issue, and it cannot be contained in one area. However, artificial environments can be developed in densely populated regions."

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global glacier melt projections 2100

Global Glaciers Face Accelerated Melting: Significant Mass Loss by 2100

Introduction: The Impact of Accelerated Glacier Retreat

The accelerated retreat of glaciers worldwide threatens significant environmental impact, including sea-level rise and the disruption of ecosystems. Researchers from ETH Zurich and Vrije Universiteit Brussel have released a comprehensive study in The Cryosphere, mapping the future of over 200,000 glaciers, excluding those in Greenland and Antarctica, under the latest climate change scenarios.

Key Findings: Projecting Glacier Mass Loss

Future Scenarios for Glacier Evolution

Lead author Harry Zekollari, formerly a postdoc at ETH Zurich's Laboratory of Hydraulics, Hydrology, and Glaciology (VAW) and now a professor at Vrije Universiteit Brussel, states, "Our modeling of glacier evolution throughout the 21st century under varying climate scenarios reveals significant differences in outcomes based on future emission trajectories."

• Optimistic Scenario: Under the most optimistic scenario of minimal emissions, glaciers may lose between 25% and 29% of their mass by the end of the century.
• High-Emission Scenario: Conversely, high-emission pathways could result in a staggering 46% to 54% loss of global glacier mass.

Regional Variations in glacier Loss

The study highlights significant regional variations in glacier loss.

• European Alps: Glaciers in the European Alps are particularly at risk, with projections indicating over 75% volume loss and potential complete disappearance under high-emission scenarios.
• Polar Regions: Arctic Canada, Iceland, and Svalbard are expected to retain a greater proportion of their glacier mass by century's end, albeit still experiencing substantial reductions.

Advancements in Glacier Modeling and Monitoring

Enhancing Precision in Glacier Projections

Daniel Farinotti, head of ETH's Professorship of Glaciology and co-author of the study, states, "This study marks an advancement over previous assessments, projecting slightly greater glacier losses than recent IPCC reports."

"The projections are based on the latest models calibrated using detailed observations for individual glaciers, as opposed to aggregated regional data. This method provides a more precise understanding of glacier-specific changes, critical for managing local water resources, mitigating natural hazards, and optimizing glacier-fed hydropower systems."

Future Advancements: Satellite Monitoring and Improved Modeling

Future advancements in satellite monitoring and glacier modeling are anticipated to significantly improve the precision of glacier projections. These innovations will provide critical data, deepening scientific insights into glaciers' climate response and supporting better planning for impacted regions globally.

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Global Freshwater Levels Plummet, NASA Satellite Data Shows

Introduction

Observations from NASA-German satellites led an international research team to discover a sharp decline in Earth's total freshwater reserves beginning in May 2014, with levels remaining consistently low. Published in Surveys in Geophysics, the findings suggest Earth's continents may now be in a sustained dry phase.

Key Findings from NASA-German Satellite Data

Decline in Freshwater Reserves (2015-2023)

Between 2015 and 2023, satellite data revealed that Earth's terrestrial freshwater storage, encompassing surface water and underground aquifers, averaged 290 cubic miles (1,2000 cubic km) less than the 2002-2014 average. "This is equivalent to losing two and a half times the volume of Lake Erie," noted Mattew Rodell, a hydrologist at NASA's Goddard Space Flight Center.

Impact of Drought and Agriculture

Periods of drought, coupled with the growing expansion of irrigated agriculture, force farms and cities to increasingly depend on groundwater, creating a feedback loop of diminishing underground reserves. With reduced rainfall and snowmelt, these freshwater sources are not replenished, prompting even greater groundwater extraction.

Global Water Stress and Implications

UN Report on Water Scarcity

A 2024 UN report on water stress highlights that diminishing water availability burdens farmers and communities, potentially triggering famine, poverty, conflicts, and heightened disease risks from contaminated water sources.

The Role of GRACE Satellites in Tracking Freshwater Decline

The Role of GRACE Satellites

Researchers pinpointed this sudden global freshwater decline through data from the Gravity Recovery and Climate Experiment (GRACE) satellites, a collaborative effort by NASA, the German Aerospace Center, and the German Research Centre for Geosciences. GRACE detects monthly gravity variations to rack changes in terrestrial water mass. The original GRACE mission operated from March 2002 to October 2017, with its successor, GRACE-Follow On (GRACE-FO), launching in May 2018.

Drought Events and Global Impact

The study reveals that the global freshwater decline was initiated by a severe drought in northern and central Brazil, followed by widespread droughts across Australasia, South America, North America, Europe, and Africa. Elevated tropical Pacific ocean temperatures from late 2014 to 2016, culminating in a significant El Niño event, disrupted atmospheric jet streams, reshaping global weather and rainfall patterns.

Persistent Freshwater Losses and the Role of Climate Change

Global Warming's Contribution

Despite the conclusion of the El Niño event, global freshwater levels did not recover. Rodell and his team note that 13 of the 30 most severe droughts observed by GRACE have occurred since January 2015. The researchers suggest that persistent freshwater losses may be linked to global warming.

Climate Change and Extreme Precipitation

Global warming increases the atmosphere's capacity to hold water vapor, intensifying precipitation events, explains NASA Goddard meteorologist Michael Bosilovich. Although annual rainfall and snowfall totals may remain relatively stable, prolonged intervals between heavy precipitation allow soil to dry and compact, reducing its capacity to absorb water during subsequent rains.

"Extreme precipitation presents a challenge," explained Bosilovich, "as water tends to run off rather than infiltrate the soil to replenish groundwater reserves." Since the 2014-2016 El Niño, global freshwater levels have remained persistently low, with a larger portion of water now retained in the atmosphere as vapor.

Rising temperatures enhance both the evaporation of water from the surface into the atmosphere and the atmosphere's capacity to hold moisture, leading to more frequent and intense droughts.

Although there are indications that the sudden decline in freshwater may be primarily driven by global warming, establishing a definitive connection between the two remains challenging, according to Susanna Werth, a hydrologist and remote sensing scientist at Virginia Tech, who was not involved in the study.

"Climate predictions carry inherent uncertainties," Werth explained. "Both measurements and models are subject to errors."

Will Freshwater Levels Recover?

It is still uncertain whether global freshwater will recover to pre-2015 levels, stabilize, or continue to decrease. Given that the nine warmest years on record align with the sharp drop in freshwater, Rodell stated, "We don't believe this is a coincidence, and it may signal what's to come."

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'Storyline' Models Reveal Global Warming's Influence on Severe Weather Events

Introduction: Storm Boris and its Impact on Central and Eastern Europe

Recently, storm 'Boris' brought intense rainfall, triggering severe flooding and disruption in Central and Eastern Europe. Analysis Wegener Institute indicates that in a cooler climate, Boris would have delivered around 9% less rain.

New Modeling Approach: The 'Storyline' Technique

What is the 'Storyline' Approach?

A new modeling approach called 'storylines' has enabled these findings, showcasing its near-real-time potential in Communications Earth & Environment. Additionally, the AWI team introduced a free online tool that allows users to detect climate change impact in extreme weather events and design their own comparative graphics.

Real-World Application: Storm Boris Case Study

In mid-September, storm 'Boris' brought intense rainfall and severe flooding to Poland, the Czech Republic, Austria, and Romania. In several areas, the rainfall marked one of the highest five-day totals on record. Tragically, at least 27 lives were lost, and countless families were displaced.

Was the Event Driven by Global Climate Change?

The Debate: Climate Change and Extreme Weather

Meanwhile, the situation has improved, and cleanup efforts continue around the clock. However, new weather extremes in Spain are already raising concerns. Once again, a central question is being debated in public, political, and media circles: Was this catastrophe driven by global climate change?

The Science of Attribution

"In recent years, science has provided solid answers to this entirely valid question," states Dr. Marylou Athanase, lead author and physicist at the Climate Dynamics Section of the Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research (AWI).

"Within just one or two weeks of an event, probabilistic attribution studies can provide initial insights into how much more likely the event was due to climate change."

The Challenge: Making Climate Impact Tangible

The Issue with Abstract Probabilities

The main issue is that probabilities tend to be abstract, especially when they intersect with tangible, exceptional real—world events. In external communications—whether to the public or policymakers-the scientific community has yet to possess a tool that can effectively demonstrate the impact of global climate change on local weather in a way that is both compelling and easy to understand.

Introducing the "What if?" Principle

"This is why, at the AWI, we've dedicated ourselves to developing an entirely new method—the 'storyline' approach," says Dr. Antonio Sánchez-Benítez, a physicist in the Climate Dynamics Section and co-lead author of the study.

"In essence, we use the 'what if?' principle—what would a specific catastrophe look like in a world without climate change? And how would it differ in a warmer climate? By contrasting these hypothetical scenarios with actual outcomes, we can clearly pinpoint the distinct impacts of climate change—not only for extreme weather but also for everyday weather patterns."

How the 'Storyline' Approach Works: The Storm Boris Example

9% Less Rainfall in a Cooler Climate

Using Storm Boris as a case study, AWI experts have now showcased the capabilities of the new approach. Their scenario comparison reveals that, in the absence of global warming, Boris would have brought approximately 9% less rainfall.

In reality, as the storm traveled from the eastern Mediterranean and the Black Sea toward Central Europe, it gained strength due to the water temperature being approximately two degrees Celsius higher than preindustrial levels. This increase led to a higher concentration of water vapor in the air over the region.

Why Even Small Changes Matter

While a 9% change may appear negligible, the true effects of intense rainfall are determined by how much water accumulates on the ground and how it is channeled. Can existing infrastructure—such as rivers, dams, or sewage systems—manage the volume, or does it overflow, resulting in extensive damage?

Bridging the Gap: Nudging for Accurate Weather Simulations

How 'Nudging' Improves Weather Models

The question arises: How did experts bridge the gap between climate models, which focus on long-term trends, and actual local weather? According to Dr. Helge Gößling, a climate physicist and team leader at AWI, the solution lies in a technique known as 'nudging.'

"Climate models typically generate a quasi-random sequence of weather patterns that align with the physical laws embedded in their programming. To detect climate variations, one must examine whether the average values and distributions shift over an extended period and across a broad range of weather conditions."

Similarly, in weather models, the simulated conditions become increasingly detached from reality after just a few weeks, limiting the accuracy of weather predictions.

Simulating a World Without Climate Change

Through 'nudging,' we incorporate real-time wind data, including jet stream patterns, to guide the model toward actual observations, enabling us to accurately replicate real-world weather within the current climate.

"Next, we modify the model's background climate, such as by simulating a world unaffected by climate change, lowering greenhouse gas concentrations, and adjusting other relevant factors, before repeating the experiment."

The Technical Backbone: AWI's Climate Model

CMIP6 and ERA5 Data Integration

The AWI climate model used is the CMIP6 version, which served as part of the foundational data for the IPCC's Sixth Assessment Report. The wind data integrated into the model is sourced from the ERA5 reanalysis by the European Centre for Medium-Range Weather Forecasts (ECMWF).

Automated Weather Analyses on Supercomputers

As Marylou Athanase explains, "We have now automated the system to the extent that daily weather analyses are conducted on the supercomputer at the German Climate Computing Center (DKRZ)."

Free Public Access: The Climate Storylines Tools

Exploring the 'Climate Changes Signal of the Day'

The data is subsequently transferred to an online tool hosted on AWI's servers, which is freely accessible to the public at climate-storylines. Analyses are performed with a three-day delay and made available online thereafter.

"Consequently, users can log in at any time to explore the 'Climate Changes Signal of the Day,' which displays global extreme and regular weather patterns. The information is presented interactively via maps and timelines, with data from January 1, 2024, onward focusing on temperature and precipitation."

Enhancing Public Understanding of Climate Change

"Our objective is to enhance understanding of the links between climate change and extreme weathers events, providing clear and timely responses that can be utilized in media coverage."

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How Many Trees for a Cooler City? Scientists Develop Urban Canopy Goal Tool

Introduction

Urban centers worldwide are grappling with intensifying heat as concrete and asphalt amplify warming effects. Tree-planting initiatives, a favored natural approach to cooling cities, have often relied on estimation rather than precise data. However, a recent study in Proceedings of the National Academy of Sciences introduces a tool that enables urban planners to establish targeted, science-backed greening objectives.

Research Overview

Lead Researchers

This research was led by Jia Wang, Weiqi Zhou, and Yuguo Qian from the Chinese Academy of Sciences, with Steward Pickett, an urban ecologist at the Cary Institute of Ecosystem Studies, contributing as a co-author.

Importance of Urban Trees

Cooling Benefits of Trees

"Trees bring multiple advantages to urban areas, with cooling being a key  one," Pickett noted. "They are particularly effective at cooling by transferring significant amounts of water from the ground to the air. As this water evaporates on the leaves' surface, it absorbs substantial heat, a process driven by evaporation physics. Additionally, the shade from trees enhances their cooling impact."

Previous Research Limitations

Focus on Localized Areas

To date, studies assessing urban trees' cooling impact primarily focus on localized areas, such as individual streets or neighborhoods. Expanding the tree canopy by 1%, for example, can lower nearby temperatures by approximately 0.04 to 0.57 degrees Celsius.

Addressing Citywide Needs

The Need for Broader Data

"This information is useful, but planners and decision-makers are thinking about citywide impacts," Pickett explained. 'They're wondering, "What tree canopy coverage does the whole city need? What happens when we increase it on a large scale?" Such data has not been accessible until now.'

Research Methodology

Assessing Cooling Efficiency

The researchers were uncertain if findings from fine—scale measurements could be applied on a citywide level. Thus, they aimed to assess how trees' cooling efficiency-defined as the temperature reduction from a 1% increase in urban canopy—varies across broader areas.

Study Cities

The researchers analyzed satellite imagery and temperature data from four climatically diverse cities:

• Beijing (Temperate)
• Shenzhen (Subtropical)
• Baltimore (Temperate)
• Sacramento in the United States (Mediterranean)

Baltimore and Beijing experience temperate climates, Shenzhen has a subtropical climate, and Sacramento falls within a Mediterranean climate zone.

Data Collection Process

1. Pixelation of Cities: The researchers begin by dividing each city into pixelated sections roughly the size of a city block.
2. Temperature and Tree Cover Measurement: For each pixel, measured the land surface temperature and tree cover.
3. Scalability of Analysis: They then expand the analysis to progressively larger areas like the neighborhood, citywide, and beyond. Finally, they calculate how the relationship between green cover and temperature referred to as cooling efficiency varies across these different scales.

Key Findings

Cooling Efficiency Across Scales

The researchers found that trees' cooling efficiency improved as the scale increased, though the rate of improvement slowed with larger unit sizes. For instance, in Beijing, a 1% increase in canopy cover at the block level lowered temperatures by approximately 0.06 degrees, while the same increase at the city scale could yield a temperature reduction of around 0.18 degrees.

Benefits of Larger Tree Collections

The additional advantages associated with larger scales seem to result form the capacity to encompass larger collections of trees, which have a greater ability to cool the environment.

Implications for Urban Planning

Predictive Capabilities

With improved insight into how area, tree canopy cover, and cooling effects interact, this research allows for the prediction of cooling impacts across entire cities.

• Framework for Managers: Equipping managers with an essential framework to establish tree canopy objectives for reducing extreme temperatures.

Power Law of Cooling Efficiency

Co-author Weiqi Zhou explains, "Our research indicates that cooling efficiency adheres to a power law across various scales, ranging from as small as 120 by 120 meters to extensive areas encompassing cities. This relationship is consistent across all four cities studied, which represent diverse climates. It implies that this model could assist in predicting the additional tree cover required to meet specific heat reduction and climate adaptation targets in urban areas globally."

Practical Applications

Case Study: Baltimore

As an example, the authors estimate that:

• Increasing tree canopy cover by 1%, Baltimore could lower land surface temperatures by 0.23°C.
• To reach a cooling target of 1.5°C, a 6.39% increase in tree canopy would be required.

Conclusion and Future Directions

Equity in Urban Tree Distribution

While this study provides critical insights for municipal-level decision-making, Pickett notes that urban planners may need to address smaller geographic scales to ensure an equitable distribution of urban trees and their benefits across the city, accompanied by community support.

Guidance on Tree Placement

"This study does not provide guidance on tree placement," Pickett remarked. "A different type of analysis would be necessary, one that incorporates comprehensive social information and collaboration with communities or individual property owners."

Future Directions

According to Pickett, potential next steps could involve extending the analysis to other cities with varying climates and investigating how effectively this nature-based solution might perform as climate change intensifies heat and aridity in some areas.

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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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