Short answers, pulled from the story.
Climate is the statistical average of weather over a thirty-year period. The World Meteorological Organization established this thirty-year period as the baseline for all modern climatological study. The organization originally set the reference frame from 1901 to 1930, later updating it to 1961 to 1990, and most recently to 1991 to 2020.
The thermohaline circulation acts as a massive conveyor belt that warms the northern Atlantic Ocean by 5 degrees Celsius compared to other ocean basins. This circulation redistributes heat between land and water on a regional scale, determining whether a city like London remains temperate while others at similar latitudes freeze. The density and type of vegetation coverage further modulate this system, affecting solar heat absorption, water retention, and rainfall patterns.
Paleoclimatologists use non-biotic evidence such as sediments found in lake beds and ice cores to provide a physical record of temperature and atmospheric composition. They also utilize biotic evidence, including tree rings and coral, to offer a biological timeline that can be read like the pages of a book. These records demonstrate periods of stability and periods of change, indicating whether shifts follow patterns such as regular cycles.
The Köppen climate classification scheme, first developed in 1899, remains the most widely used method. It correlates closely with biome classification to identify the climates associated with certain plant life. The Thornthwaite system, in use since 1948, incorporates evapotranspiration along with temperature and precipitation information, making it essential for studying biological diversity and how climate change affects it.
The launch of satellites in the 1960s allowed records to be gathered on a global scale, including areas with little to no human presence such as the Arctic region and oceans. This technological leap provided a comprehensive view of the Earth's energy balance, revealing the Earth's Energy Imbalance as a fundamental metric of the status of global change. The data collected from these modern instruments shows that average global air temperature has passed 1.5 degrees Celsius of warming in the period from February 2023 to January 2024.
The primary driver for increased global temperatures in the industrial era is human activity, with natural forces adding variability to the mix. The United Nations Framework Convention on Climate Change uses the term climate change to refer to changes in modern climate, including the rise in average surface temperature known as global warming, with a presumption of human causation. The emission of greenhouse gases by human activities occurs on a much faster time scale than naturally caused changes, leading to a rapid redistribution of biota.