By Jim Steele
A year ago, while passing through Huntsville, Alabama, I had the great fortune of sitting down with Roy Spencer and John Christy for an enjoyable extended lunch. As we were leaving, John gave me his new book, “Is it getting hotter in Fresno… or not?“The city of Fresno may not resonate with most people, but having studied the impact of climate on ecosystems in California for 30 years, I know it will be an invaluable contribution to our understanding. I. On the cover is a boy gazing at the sky, so I hope that also means John will explain climate change at the recommended 6order to better reach the public.
But climate change is complex and cannot be explained by any simple magic knob. A better title for his book would be “How honest scientists adjust temperature data and assess trends.” The boy on the cover represents John’s life as a “weather enthusiast” with a constant desire to learn about climate and weather since middle school. Throughout the book, Christy’s uncompromising integrity is evident as he spends several chapters explaining how and why temperature data MUST be adjusted before any comparisons between stations. weather can be meaningfully evaluated. He readily admits however that those adjustments are part science and part art form, requiring a thorough knowledge of the landscape surrounding each weather station. Without understanding those landscape effects, Christy warns “the adjustment process is heavily influenced by what the scientist expects. So instead of objective information, we have predefined information >”
You may need to double-read the chapters on why temperature regulation is needed, but I highly recommend you do. It shows how different landscapes, natural or altered, affect the weather. That will help you separate the good adjustments from the bad ones. Christy has seen first-hand how each change in the location of the weather station in Fresno has taken it to a new perspective. He has witnessed the growing effects of urbanization on various parts of the region. Too many climate skeptics easily assume that all adjustments are driven by political bias. Indeed, without exhaustive knowledge of changes in the surrounding landscape, applying a one-size-fits-all algorithm and the expectation that any warming must be due to increased CO , will inevitably distort the temperature regulation. But good skeptic climate scientists, like John Christy, understand that there are a number of important variables that affect weather and that need to be fine-tuned.
Although Fresno’s weather is of little interest to most people, especially if they’ve never been there, I can’t wait to read John’s analysis. Fresno is just 60 miles southwest of Yosemite National Park, where I studied climate during my research into northern California’s wildfires and ecosystems. Fresno is a growing city surrounded by grasslands of the San Joaquin Valley 300 feet above sea level, where wetlands are lost and irrigation affects temperatures. In winter, Fresno is plagued by lingering fog, while the forests of Yosemite are shrouded in snow at 4,000 feet. However, like Christy’s analysis of Fresno’s temperature trends, the American Historical Climatology network determined that Yosemite’s maximum temperature did not warm at all, on the contrary, the minimum temperature increased significantly. Similar warmer maximum temperature shortfalls since 1930 have been reported for all of northern California.
Using Christy’s correction method, Fresno’s maximum temperature fell as much as Yosemite’s between 1930 and 2010, while the operating minimum was very different, warming steadily. After calculating the effects of urbanization, he concluded, “I am more confident that Fresno’s natural climate has not warmed in the last 130 years and that the upper limit of the natural TMAX (maximum temperature) will at about +0.05°F/decade. And despite the increase since 2010, there is no statistically significant daytime warming in Fresno.
In contrast, minimum temperatures have increased significantly by 0.51°F/decade. As illustrated in the light of the satellite image, the current location of the Fresno weather station (KFAT) is Fresno Airport located in the heart of the increasingly thermal urban island of Fresno. Due to human change to that landscape, KFAT is now 6°F warmer than it was in the late 1880s. It’s clear that maximum and minimum temperatures are being driven by different dynamics. So they should be analyzed separately as Christy did. The average maximum and minimum temperatures produce an average that is as biased as the mean for apples and oranges.
Finally, Christy looks at trends in extreme temperatures using different thresholds. One such analysis examined the number of days per decade when maximum temperatures exceeded 99.5°F (orange bars). As predicted from trend analysis, extremely hot days have become less and less common since 1880. Although there has been a recent surge, there are still more hot days than in the 1930s. And like an island The growing urban heat island will also predict, the number of days when the minimum temperature falls below 32.5°F, has steadily decreased (blue bars).
For those interested in how to build temperature trends, I highly recommend Christy’s book. A thorough examination of Fresno’s temperatures reveals no climate crisis. But for those living within Fresno’s city limits, efforts to alleviate the sweltering heat caused by urban heat islands, would be well-spent.