4b

• Climate change


  The overall climate of the planet is changing extremely rapidly, driven by anthropogenic actions affecting the climate
• Climate change is already generating extremes of weather and affecting organisms of all kinds, and effects are likely to get much stronger
• The last 500 million years


  • Major periods of warming and cooling, with an overall pattern of cooling for the last 100 million years
• Current climate phase


  We are in a warm phase of a cool period, with occasional dips in temperature
• The eruption of the Indonesian volcano Tambora in 1815 led to a "year without summer" in Europe, with snow and frost in June/July
• Major disturbances to modern ecosystems and habitats

  • Pollution
  • Habitat fragmentation
  • Acid rain
  • Deforestation
  • Overfishing
• Many changes are ultimately driven by climate change, and the primary issue there is the build-up of greenhouse gases
• Greenhouse gases


  Carbon dioxide, water vapor, ozone, CFCs, and especially methane
• Carbon dioxide is the biggest contributor to greenhouse gas emissions, produced by human activities
• Greenhouse gases


  • Methane is emitted in lower concentrations than CO2 but is much more powerful as a greenhouse gas
  • Some gases spend years or even decades in the atmosphere
• • Methane is approximately 30 times more effective than CO2 at trapping heat over 100 years, and 84 times more effective over 20 years
  • Nitrous oxide is 264 times stronger than CO2 over short and long periods
• All the 10 warmest years on record are the last 10, with 2023, 2016, 2019, 2020, 2015, 2022, 2021, 2017, 2018, 2014 being the top 10
• During the last 50 years, there is >90% probability of cold days/nights & frost decreasing, and >66% probability of heat waves, heavy precipitation events, and extreme high sea levels increasing

  
• The IPCC has stated that most of the observed increase in global average temperatures since the mid-20th century is very likely (>90% in 2007, >99% in 2013) due to the observed increase in anthropogenic greenhouse gas concentrations

  
• Consequences of global warming

  • Reduction in sea ice and glaciers
  • Rising sea levels
  • Changing sea temperatures and acidification
  • Desertification
  • Changes in weather patterns
• Over the last 40 years, there has been a 40% decrease in Arctic sea ice, and ice-free summers may be coming soon

  
• The reduction in sea ice leads to a reduction in albedo, further accelerating warming

  
• Current sea level rise is just 3 mm a year, around 80% faster than recent centuries, and some estimates project an increase of 2 m by the end of this century

  
• Huge amounts of carbon dioxide have been absorbed by the oceans, turning them acidic and causing problems for many marine animals, especially those that use calcification reactions
• There have been increases in extreme weather events such as floods, droughts, very cold winters, heatwaves, and forest fires
• From 2000-2012, roughly 30 to 70 percent of the U.S. land area experienced conditions that were at least abnormally dry at any given time, though it has overall been relatively wetter than average

  
• Overgrazing and improper land use are causing desertification through loss of plants that bind soils, allowing for rapid erosion and increased insolation, further accelerated by increasing temperatures
• Even with no more CO2 produced, temperatures would continue to rise

  
• The greatest changes in the UK are in summer and especially in winter, with changes greater in the south
• For the 2080 Medium Emission Scenario, it will continue to get warmer and that will bring still more weather extremes
• Possible responses of populations and species to climate change

  • Move
  • Tolerate
  • Evolve
  • Die
• Movement


  As environments change and/or are lost, species may be forced to relocate or go extinct, with some already moving to higher latitudes or altitudes in response to increasing temperatures
• Toleration


  Species may be able to survive locally to changing conditions, through evolution in response to new selective pressures or adaptation, or by using differing microhabitats
• We are seeing changes in the timing of biological events like earlier frog breeding, cherry blossom, and oak leaf unfurling
• The conditions of the planet are changing at an unprecedented rate, with profound effects across the globe in all environments and habitats, in addition to other issues like pollution, acid rain, overfishing, deforestation, and extinctions