3/27/2023 0 Comments Hows weather up here scienceThis stability enabled agriculture, permanent settlements and population growth. The last 8,000 years, which includes most recorded human history, have been relatively stable at the warmer end of this temperature range. In the coldest period of the last ice age, about 20,000 years ago, sea level was at least 120 metres lower than today because more water was locked up on land in polar ice sheets. Over the past million years, Earth’s globally averaged surface temperature has risen and fallen by about 5˚C in ice-age cycles, roughly every 100,000 years or so (Figure 2.1a). Several million years ago, for example, global average temperature was a few degrees higher than today and warm, tropical waters reached much farther from the equator, resulting in very different patterns of ocean and atmospheric circulation from today. Natural variations in the concentrations of greenhouse gases in the atmosphere, the evolution of life and meteorite impacts have also caused climate change in the past. These changes have been triggered by the changing configuration of continents and oceans, changes in the Sun’s intensity, variations in the orbit of Earth, and volcanic eruptions. Visualisation: NASAĮarth’s climate has changed dramatically many times since the planet was formed 4.5 billion years ago. NASA’s Global Precipitation Measurement (GPM) Core Observatory satellite is designed to provide rain and snow observations worldwide. Photo: ©/John Carnemolla Past climate has varied enormously on a variety of time-scales Scientists have been using specialised equipment to measure and record weather and climate since 1850. How has climate changed? Aerial view of the Norman River flowing towards the Gulf of Carpentaria in far north Queensland. However, this equation was obtained using a multiple regression analysis, and therefore, it has an error of ☑.3 ° F. If you're really mathematically inclined, there is an equation that gives a very close approximation to the heat index. Use this weather calculator if you prefer to enter numbers manually instead of reading a chart. Heat cramps or heat exhaustion likely, and heat stroke possible with prolonged exposure and/or physical activity Heat stroke, heat cramps, or heat exhaustion possible with prolonged exposure and/or physical activity As shown in the table below, heat indices meeting or exceeding 103 ° F can lead to dangerous heat disorders with prolonged exposure and/or physical activity in the heat.įatigue possible with prolonged exposure and/or physical activity If you are exposed to direct sunlight, the heat index value can be increased by up to 15☏. It surprises many people to learn that the heat index values in the chart above are for shady locations. A full heat index chart for a larger range of temperatures and relative humidity values can be found at this link. In the Panhandles, we commonly see hot temperatures during the summer, but the low relative humidity values make it somewhat unusual to see dangerous heat index values (i.e. For example, if the air temperature is 100 ° F and the relative humidity is 15%, the heat index is 96 ° F ( use this calculator). When the relative humidity is low, the apparent temperature can actually be lower than the air temperature. For example, if the air temperature is 100 ° F and the relative humidity is 55%, the heat index will be 124 ° F. In order to determine the heat index using the chart above, you need to know the air temperature and the relative humidity. There is direct relationship between the air temperature and relative humidity and the heat index, meaning as the air temperature and relative humidity increase (decrease), the heat index increases (decreases). The body actually feels cooler in arid conditions. The opposite is true when the relative humidity decreases because the rate of perspiration increases. In other words, the human body feels warmer in humid conditions. relative humidity) is high, the rate of evaporation from the body decreases. When the atmospheric moisture content (i.e. When perspiration is evaporated off the body, it effectively reduces the body's temperature. If the perspiration is not able to evaporate, the body cannot regulate its temperature. When the body gets too hot, it begins to perspire or sweat to cool itself off. This has important considerations for the human body's comfort. The heat index, also known as the apparent temperature, is what the temperature feels like to the human body when relative humidity is combined with the air temperature. That's a partly valid phrase you may have heard in the summer, but it's actually both.
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