Climate change

From Wikipedia, the free encyclopedia

For a discussion of climate trends throughout Earth's history, see Climate variability and change. (further downpage)

Climate change includes both the global warming driven by human emissions of greenhouse gases, and the resulting large-scale shifts in weather patterns.[1] Though there have been previous periods of climatic change, since the mid-20th century the rate of human impact on Earth's climate system and the global scale of that impact have been unprecedented.[2]

That human activity has caused climate change is not disputed by any scientific body of national or international standing.[3] The largest driver has been the emission of greenhouse gases, of which more than 90% are carbon dioxide (CO2) and methane.[4] Fossil fuel burning for energy consumption is the main source of these emissions, with additional contributions from agriculturedeforestation, and industrial processes.[5] Temperature rise is accelerated or tempered by climate feedbacks, such as loss of sunlight-reflecting snow and ice cover, increased water vapour (a greenhouse gas itself), and changes to land and ocean carbon sinks.

Because land surfaces heat faster than ocean surfaces, deserts are expanding and heat waves and wildfires are more common.[7] Surface temperature rise is greatest in the Arctic, where it has contributed to melting permafrost, and the retreat of glaciers and sea ice.[8] Increasing atmospheric energy and rates of evaporation cause more intense storms and weather extremes, which damage infrastructure and agriculture.[9] Rising temperatures are limiting ocean productivity and harming fish stocks in most parts of the globe.[10] Current and anticipated effects from undernutrition, heat stress and disease have led the World Health Organization to declare climate change the greatest threat to global health in the 21st century.[11] Environmental effects include the extinction or relocation of many species as their ecosystems change, most immediately in coral reefsmountains, and the Arctic.[12] Even if efforts to minimize future warming are successful, some effects will continue for centuries, including rising sea levels, rising ocean temperatures, and ocean acidification from elevated levels of CO2.[13]

Many of these effects are already observed at the current level of warming, which is about 1.1 °C (2.0 °F).[15] The Intergovernmental Panel on Climate Change (IPCC) has issued a series of reports that project significant increases in these impacts as warming continues to 1.5 °C (2.7 °F) and beyond.[16] Under the Paris Agreement, nations agreed to keep warming "well under 2.0 °C (3.6 °F)" by reducing greenhouse gas emissions. However, under those pledges, global warming would reach about 2.8 °C (5.0 °F) by the end of the century, and current policies will result in about 3.0 °C (5.4 °F) of warming.[17] Limiting warming to 1.5 °C (2.7 °F) would require halving emissions by 2030, then reaching near-zero levels by 2050.[18]

Mitigation efforts include the research, development, and deployment of low-carbon energy technologies, enhanced energy efficiency, policies to reduce fossil fuel emmissions,  reforestation, and forest preservationClimate engineering techniques, most prominently  solar radiation management and carbon dioxide removal, have substantial limitations and carry large uncertainties. Societies and governments are also working to adapt to current and future global-warming effects through improved coastline protection, better disaster management, and the development of more resistant crops.

Climate variability and change

From Wikipedia, the free encyclopedia

For the current rise in Earth's average temperature and its effects, see Climate change. (above)

Climate variability includes all the variations in the climate that last longer than individual weather events, whereas the term climate change only refers to those variations that persist for a longer period of time, typically decades or more. In the time since the industrial revolution the climate has increasingly been affected by human activities that are causing global warming and climate change.[1]

The climate system receives nearly all of its energy from the sun. The climate system also radiates energy to outer space. The balance of incoming and outgoing energy, and the passage of the energy through the climate system, determines Earth's energy budget. When the incoming energy is greater than the outgoing energy, earth's energy budget is positive and the climate system is warming. If more energy goes out, the energy budget is negative and earth experiences cooling.

The energy moving through Earth's climate system finds expression in weather, varying on geographic scales and time. Long-term averages and variability of weather in a region constitute the region's climate. Such changes can be the result of "internal variability", when natural processes inherent to the various parts of the climate system alter the distribution of energy. Examples include variability in ocean basins such as the Pacific decadal oscillation and Atlantic multidecadal oscillation. Climate variability can also result from external forcing, when events outside of the climate system's components nonetheless produce changes within the system. Examples include changes in solar output and volcanism.

Climate variability has consequences for sea level changes, plant life, and mass extinctions; it also affects human societies.

​​​​​​​​Climate Science for Beginners Part 3

​​​Last Year's 25th November Announcement: A Fitting Reminder...

​​​The Arctic's sweltering 2020 continues in earnest with temperatures last weekend reaching more than 5° (12°F) above the norm for the 1990s. In some isolated pockets, the temperature is more than 20°C (30 - 40F) above the expected average.