TEMPERATURE RISE

 Introduction

Over the last 50 years, human activities – particularly the burning of fossil fuels – have released sufficient quantities of carbon dioxide and other greenhouse gases to trap additional heat in the lower atmosphere and affect the global climate.

In the last 130 years, the world has warmed by approximately 0.85oC. Each of the last 3 decades has been successively warmer than any preceding decade since 1850

 The planet is warming, from North Pole to South Pole.  And the impacts of rising temperatures aren’t waiting for some far-flung future–the effects of global warming are appearing right now. The heat is melting glaciers and sea ice, shifting precipitation patterns, and setting animals on the move. Sea levels are rising, glaciers are melting and precipitation patterns are changing. Extreme weather events are becoming more intense and frequent.

The Past & The Future

The 10 warmest years on record have all occurred since 2005, and 7 of the 10 have occurred just since 2014. Looking back to 1988, a pattern emerges: except for 2011, as each new year is added to the historical record, it becomes one of the top 10 warmest on record at that time, but it is ultimately replaced as the “top ten” window shifts forward in time.

By 2020, models project that global surface temperature will be more than 0.5°C (0.9°F) warmer than the 1986-2005 average, regardless of which carbon dioxide emissions pathway the world follows. This similarity in temperatures regardless of total emissions is a short-term phenomenon: it reflects the tremendous inertia of Earth's vast oceans. The high heat capacity of water means that ocean temperature doesn't react instantly to the increased heat being trapped by greenhouse gases. By 2030, however, the heating imbalance caused by greenhouse gases begins to overcome the oceans' thermal inertia, and projected temperature pathways begin to diverge, with unchecked carbon dioxide emissions likely leading to several additional degrees of warming by the end of the century.

" 2019 among the three warmest years on record" 

Many characteristics of climate change directly depend on the level of global warming, but what people experience is often very different to the global average. For example, warming over land is larger than the global average, and it is more than twice as high in the Arctic.

But it is not just about temperature. Climate change is bringing multiple different changes in different regions – which will all increase with further warming. These include changes to wetness and dryness, to winds, snow and ice, coastal areas and oceans. For example:

• Climate change is intensifying the water cycle. This brings more intense rainfall and associated flooding, as well as more intense drought in many regions.
• Climate change is affecting rainfall patterns. In high latitudes, precipitation is likely to increase, while it is projected to decrease over large parts of the subtropics. Changes to monsoon precipitation are expected, which will vary by region.
• Coastal areas will see continued sea level rise throughout the 21st century, contributing to more frequent and severe coastal flooding in low-lying areas and coastal erosion. Extreme sea level events that previously occurred once in 100 years could happen every year by the end of this century.
• Further warming will amplify permafrost thawing, and the loss of seasonal snow cover, melting of glaciers and ice sheets, and loss of summer Arctic sea ice.
• Changes to the ocean, including warming, more frequent marine heatwaves, ocean acidification, and reduced oxygen levels have been clearly linked to human influence. These changes affect both ocean ecosystems and the people that rely on them, and they will continue throughout at least the rest of this century.
• For cities, some aspects of climate change may be amplified, including heat (since urban areas are usually warmer than their surroundings), flooding from heavy precipitation events and sea level rise in coastal cities.

Impact of Temperature Rise 

• Ice is melting worldwide, especially at the Earth’s poles. This includes mountain glaciers, ice sheets covering West Antarctica and Greenland, and Arctic sea ice. In Montana's Glacier National Park the number of glaciers has declined to fewer than 30 from more than 150 in 1910.
• Much of this melting ice contributes to sea-level rise. Global sea levels are rising 0.13 inches (3.2 millimeters) a year, and the rise is occurring at a faster rate in recent years.
• Rising temperatures are affecting wildlife and their habitats. Vanishing ice has challenged species such as the Adélie penguin in Antarctica, where some populations on the western peninsula have collapsed by 90 percent or more.
• As temperatures change, many species are on the move. Some butterflies, foxes, and alpine plants have migrated farther north or to higher, cooler areas.
• Precipitation (rain and snowfall) has increased across the globe, on average. Yet some regions are experiencing more severe drought, increasing the risk of wildfires, lost crops, and drinking water shortages.
• Some species—including mosquitoes, ticks, jellyfish, and crop pests—are thriving. Booming populations of bark beetles that feed on spruce and pine trees, for example, have devastated millions of forested acres in the U.S.

Other effects could take place later this century, if warming continues. These include:

• Sea levels are expected to rise between 10 and 32 inches (26 and 82 centimeters) or higher by the end of the century.
• Hurricanes and other storms are likely to become stronger. Floods and droughts will become more common. Large parts of the U.S., for example, face a higher risk of decades-long "megadroughts" by 2100.
• Less freshwater will be available, since glaciers store about three-quarters of the world's freshwater.
• Some diseases will spread, such as mosquito-borne malaria (and the 2016 resurgence of the Zika virus).
• Ecosystems will continue to change: Some species will move farther north or become more successful; others, such as polar bears, won’t be able to adapt and could become extinct.

REFERENCES: 

• USGCRP, 2017: Climate Science Special Report: Fourth National Climate Assessment, Volume I [Wuebbles, D.J., D.W. Fahey, K.A. Hibbard, D.J. Dokken, B.C. Stewart, and T.K. Maycock (eds.)]. U.S. Global Change Research Program, Washington, DC, USA, 470 pp., doi: 10.7930/J0J964J6.
• NOAA National Centers for Environmental Information, State of the Climate: Global Climate Report for Annual 2020, online January 2021, retrieved on March 15, 2021 from https://www.ncdc.noaa.gov/sotc/global/202013.
•  IPCC, 2014: Summary for Policymakers. In: Climate Change 2014: Mitigation of Climate Change.
• who.int/
• https://www.nationalgeographic.com/
• https://www.ipcc.ch/