Query: Droughts and floods have not changed since weve been using fossil fuels

Relevant passages:
Effects of global warming <=SEP=> The effects of global warming are the environmental and social changes caused ( directly or indirectly ) by human emissions of greenhouse gases . There is a scientific consensus that climate change is occurring , and that human activities are the primary driver . Many impacts of climate change have already been observed , including glacier retreat , changes in the timing of seasonal events ( e.g. , earlier flowering of plants ) , and changes in agricultural productivity .   Future effects of climate change will vary depending on climate change policies and social development . The two main policies to address climate change are reducing human greenhouse gas emissions ( climate change mitigation ) and adapting to the impacts of climate change . Geoengineering is another policy option .   Near-term climate change policies could significantly affect long-term climate change impacts . Stringent mitigation policies might be able to limit global warming ( in 2100 ) to around 2 ° C or below , relative to pre-industrial levels . Without mitigation , increased energy demand and extensive use of fossil fuels might lead to global warming of around 4 ° C. Higher magnitudes of global warming would be more difficult to adapt to , and would increase the risk of negative impacts .

History of the world <=SEP=> The history of the world ( or world history ) describes the history of humanity ( or human history ) as determined by the study of archaeological and written records , beginning with the invention of writing .   The roots of civilization reach back to the earliest introduction of primitive technology and culture , while Prehistory begins in the Palaeolithic Era , or `` Early Stone Age '' , which is followed by the Neolithic Era , or `` New Stone Age '' , and the Agricultural Revolution ( between 8000 and 5000 BCE ) in the Fertile Crescent . The latter period marked a change in human history , as humans began the systematic husbandry of plants and animals . Agriculture advanced , and most humans transitioned from a nomadic to a settled lifestyle as farmers in permanent settlements . Nomadism continued in some locations , especially in isolated regions with few domesticable plant species , but the relative security and increased productivity provided by farming allowed human communities to expand into increasingly larger units , fostered by advances in transportation .   As farming developed , grain agriculture became more sophisticated and prompted a division of labour to store food between growing seasons . Labour divisions then led to the rise of a leisured upper class and the development of cities . The growing complexity of human societies necessitated systems of writing and accounting . Many cities developed on the banks of lakes and rivers as early as 3000 BCE , when some of the first prominent , well-developed settlements had arisen in Mesopotamia ( `` the Land between the Rivers '' ) , on the banks of Egypt 's Nile River , in the Indus River valley , and along the rivers of China .   The history of the Old World ( particularly Europe and the Mediterranean ) is commonly divided into ancient history ( or `` Antiquity '' ) , up to 476 CE ; post-classical history ( or `` the Middle Ages '' ) , from the 5th through 15th centuries , including the rise of Christianity , the Islamic Golden Age ( c. 750 CE -- c. 1258 CE ) and the early Italian Renaissance ( beginning around 1300 CE ) ; the early modern period , from the 15th century to the late 18th , including the Age of Enlightenment ; and the late modern period , from the Industrial Revolution to the present , including contemporary history .   In the mid-15th century , the invention of modern printing , employing movable type , revolutionized communication , helping end the Middle Ages and ushering in the Scientific Revolution . By the 18th century , the accumulation of knowledge and technology , especially in Europe , had reached a critical mass that brought about the Industrial Revolution . Outside the Old World , including ancient China and ancient India , historical timelines unfolded differently . However , by the 18th century , due to extensive world trade and colonization , the histories of most civilizations had become substantially intertwined ( see `` Globalization '' ) . In the last quarter-millennium , the rates of growth of population , knowledge , technology , communications , commerce , weapons destructiveness and environmental degradation have greatly accelerated , creating opportunities and perils that now confront the planet 's human communities .

Drought <=SEP=> A drought is a period of below-average precipitation in a given region , resulting in prolonged shortages in its water supply , whether atmospheric , surface water or ground water . A drought can last for months or years , or may be declared after as few as 15 days . It can have a substantial impact on the ecosystem and agriculture of the affected region and harm to the local economy . Annual dry seasons in the tropics significantly increase the chances of a drought developing and subsequent bush fires . Periods of heat can significantly worsen drought conditions by hastening evaporation of water vapour .   Many plant species , such as those in the family Cactaceae ( or cacti ) , have drought tolerance adaptations like reduced leaf area and waxy cuticles to enhance their ability to tolerate drought . Some others survive dry periods as buried seeds . Semi-permanent drought produces arid biomes such as deserts and grasslands . Prolonged droughts have caused mass migrations and humanitarian crises . Most arid ecosystems have inherently low productivity . The most prolonged drought ever in the world in recorded history occurred in the Atacama Desert in Chile ( 400 Years ) .