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From ancient times, people suspected that the climate of a region could change over the course of centuries. For example, Theophrastus, a pupil of Ancient Greek philosopher Aristotle in the 4th century BC, told how the draining of marshes had made a particular locality more susceptible to freezing, and speculated that lands became warmer when the clearing of forests exposed them to sunlight.
The past half-century has produced some of the most significant and astounding inventions ever developed in human history, and many notable ones came to life in the United States.
The increase of stratification in the upper ocean during the second half of the 21st century can lead to a decoupling between the surface and the deeper oceans. [14] This decoupling can cause de-oxygenation in the deeper ocean as well, since the decoupling makes it less likely for the oxygen to reach the deeper oceans.
36th century BC: 35th century BC: 34th century BC: 33rd century BC: 32nd century BC: 31st century BC: 3rd millennium BC · 3000–2001 BC 30th century BC: 29th century BC: 28th century BC: 27th century BC: 26th century BC: 25th century BC: 24th century BC: 23rd century BC: 22nd century BC: 21st century BC: 2nd millennium BC · 2000–1001 BC ...
Jacobshavn Isbræ in west Greenland, a major outlet glacier of the Greenland Ice Sheet, was the fastest moving glacier in the world over the past half century. It had been moving continuously at speeds of over 24 m (79 ft) per day with a stable terminus since at least 1950.
The current multi-century period is the warmest in the past 100,000 years. [3] The temperature in the years 2011-2020 was 1.09 °C higher than in 1859–1890. The temperature on land rose by 1.59 °C while over the ocean it rose by 0.88 °C. [3] In 2020 the temperature was 1.2 °C above the pre-industrial era. [4]
Callendar presented evidence that both temperature and the CO 2 level in the atmosphere had been rising over the past half-century, and he argued that newer spectroscopic measurements showed that the gas was effective in absorbing infrared in the atmosphere. Nevertheless, most scientific opinion continued to dispute or ignore the theory.
Groups of children have been followed from the womb to adulthood, and higher childhood blood lead levels are consistently associated with higher adult arrest rates for violent crimes. All of these studies tell the same story: Gasoline lead is responsible for a good share of the rise and fall of violent crime over the past half century. [8]