Weather & Climate
The earth's tilt, rotation and land/sea distribution affect the global weather patterns we observe. While the weather varies from day-to-day at any particular location, over the years, the same type of weather will reoccur. The reoccurring "average weather" found in any particular place is called climate. Weather measurements (maximum temperature, minimum temperature, wind speed and direction, rainfall, etc.) for any place, for any day, over a fixed number of years, determines the average weather. Averaged weather values represent the climatic normal weather for that day. From the National Centers for Environmental Information: "the climatic normal is simply the arithmetic average of the values over a 30-year period. The current set of climate normals is based upon observed weather in the years of 1981 to 2010. In 2021, a new set of climate normals will be generated based upon the observed weather between 1991 and 2020.”
Climate change is the most threatening effect of recent human activities. For example, climate scientists have hypothesized that Arctic sea ice decline, reduced snow cover, changing evaporation patterns, and other weather anomalies are expected to make the Arctic heat up faster than other parts of the globe.
Weather in its simplest form is the expression of heating and cooling effects. When wind blows the roof off a house, the energy required was supplied by the sun. The energy may have been stored briefly in the water of a lake or ocean and then expressed through evaporation of the water and heating of the air. Air moves when there is a pressure gradient that is another result of heating and cooling. The water vapor content of the atmosphere will increase in a greenhouse-warmed world. With more water vapor in the atmosphere and an increase in sea surface temperatures, there will be increased precipitation at times and more vigorous storms and floods. The attempt to understand complex systems has taken a quantum leap in recent years. We have gone beyond naïve linear models and now appreciate that if complex systems such as the atmosphere, the oceans, and land ecosystems change, they may become unstable and more unfriendly.
Heat drives weather and increased heat means warmer ocean water and turbulence in the atmosphere. The consequences of increased greenhouse gases have to do with the distribution of this extra heat and its effect on ocean and air circulation patterns. We can accept paradoxical weather results as the extra heat is unevenly distributed and makes weather more unstable.
The warmest years on record since instrumental climate records began in 1850 were 1998, 2005, 2010 and 2016. Warming continues in 2017 with heat waves, droughts, hurricanes and forest fires. The average global sea-surface and land-surface air temperature from December 2007 to November 2008 was 14.3 °C according to the World Meteorological Organization. The 2013 global average ocean temperature was 0.48°C (0.86°F) above the 20th century average of 16.1°C (60.9°F) and tied with 2006 as the eighth highest annual temperature on record and the highest since 2010. In 2016, the world's surface was warmer than average and, in some locations, record warm during August 2015, contributing to the monthly global record warmth. The combined average temperature over global land and ocean surfaces for August 2015 was 0.88°C (1.58°F) above the 20th century average of 15.6°C (60.1°F) and the highest August in the 136-year record. The WMO temperature analysis is based on land-based weather stations in 188 countries, complemented by measurements from ships, buoys and satellites. NASA’s Goddard Institute for Space Studies and the UK Met Office both contributed their own data to the WMO analysis and independently arrived at similar determinations of surface temperature.