Resolution 7478 hazard mitigation

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2024 Hennepin County All -Jurisdiction Hazard Mitigation Plan Volume 2 — Hazard Inventory has been observed throughout the year with increased frequency during recent decades. Most notably, in 2021 latest date a 50' F dew point had ever been recorded at the Twin Cities long-term station advanced 10 days, to December 151h, in 2021, and then 10 more days, to December 251h in 2023. The latest 60' dew point on record was measured on November 101h of 2022. The earliest date to measure 50' F was February 20, 2017, and the earliest 60' F dew point occurred on March 17, 2012. Increased humidity is not just a human comfort concern; it also has implications for precipitation and severe weather frequency, because water vapor is what fuels precipitating weather systems. The high dew points recorded on December 15, 2021, were associated with an unprecedented winter outbreak of tornadoes and damaging thunderstorm winds in southeastern Minnesota. The December 25, 2023, high dew points were associated with an unusually heavy December rainfall event. The 60' F dew point on March 17, 2012, was matched or nearly matched for several more days, and fueled a rash of rare mid - March severe thunderstorms across Minnesota. 4.3.1.2. Range of Magnitude Climate change is unlike other hazards because it is not episodic and does not "strike." Rising global temperatures represent a constant and increasing force that is always present, even when it is not obviously detectable in each weather pattern or climatological data set. The magnitude of climate change is generally measured as the total warming of the earth's atmosphere above "pre -industrial" temperatures, with that period reflecting 1850-1900 averages in some data sets, or simply beginning in 1880 in other data sets. These temperatures are closely, but not exclusively linked to the global concentrations of carbon dioxide, as measured at the Mauna Loa observatory in Hawaii. Carbon dioxide levels have increased annually for decades, but while global temperatures have increased steadily, natural factors, like El Nino and some ocean circulation phenomena, drive normal fluctuations the global heat content. Virtually all data sets show that the earth has warmed between 1.1° and 1.3° C (2 — 2.3° F), and most show a continued warming rate 0.1 to 0.2° C (.18° to 0.36' F) per decade. These warming magnitudes and rates are smoothed to remove the influence of large short-term variations, including the world -record temperature spikes observed in 2023, when global temperatures exceeded 1.5° C above pre -industrial levels at times, and when the average anomaly was 1.3° to 1.54' C for the year. Translating the magnitude of warming globally, into weather or climate impacts experienced in Hennepin County is not straightforward. The science of "attribution," or determining how much of a given trend, change, or event, is attributable to human -caused climate change, has largely focused on events that to date have not included the area. These studies usually indicate that climate change is responsible for all, or nearly all long-term warming in non -urbanized areas, and that it enhances or intensifies some types of extreme weather events but does not "cause" them. Given that the Twin Cities airport climate station is and has always been in an urban, built-up area, we know that some of the temperature increase seen there is because of urban "heat island" effects and not the changing global climate. At rural stations, and in homogenized data sets like the county -averaged one 54