Evidence of Climate Change (Changing patterns of Climate)

Global Warming and Climate Impact Drivers

• Global temperatures have risen steadily since 1880

• Impacts of warming include:

  • More intense heat waves

  • Warmer nights

  • Longer growing seasons

  • Fewer frost days

  • Earlier arrival of spring

  • Increased frequency and severity of floods and storms

• These changes are known as climate impact drivers (CIDs)

• CIDs are influenced by natural regional climate variations

• While single events may have natural causes, the global pattern change reflects added energy in the atmosphere and oceans

Climatic Impact Drivers (CIDs)

• CIDs are physical climate system conditions (e.g., data events, extremes) that affect an element of society or ecosystems

• CIDs can be detrimental, beneficial, neutral, or a mixture of each across interacting system elements and regions

• Multiple climatic impact-drivers are projected to change in all regions of the world

Changes in Diurnal Temperature

• Diurnal temperature is the variation in temperature within a single day

• It is the difference between daily maximum (daytime) and minimum (nighttime) temperatures

• In the context of climate change

  • Both daytime and nighttime temperature extremes are increasing

  • Nighttime temperatures are rising faster than daytime temperatures

  • Cause: Increased greenhouse gases (e.g., water vapor and CO2)

  • These gases trap heat and slow radiative heat loss at night

  • This trend is direct evidence that greenhouse gas emissions are altering the Earth’s energy balance in the troposphere

  • Impact 1.5 degrees C on daytime and 2.5 degrees C on nighttime

Changes in precipitation

• Warmer air holds ~7% more water vapor per 1 degree C, fueling more rainfall

• Warming atmosphere and oceans alter natural climate cycles, affecting regional climates

• Global warming leads to:

  • More intense precipitation events

  • Higher frequency of heavy rainfalls

  • Not always an increase in overall precipitation amount

• Regional trends:

  • U.S. precipitation rose ~5% since 1910

  • Upper midwest: precipitation frequency rose 20%, wet days rose 50% since 1900

• Difficult to separate climate change signals from natural variability

• Extreme floods linked to warming:

  • Europe (2007,2021)

  • West Africa, Uganda, Sudan, Kenya, Ethiopia, australian, Pakistan (2010-2011)

  • U.S. (Hurricanes Harvey 2017, Michael 2018, Ida 2021)

Droughts and Fires

• Definition (NOAA):

  • A period of unusually persistent dry weather that persists long enough to cause serious problems such as crop damage and/or water supply shortages

• Key drivers of mutidecadal drought:

  • Global: Atmospheric & oceanic circulation patterns

  • Regional: Temperature, precipitation, evaporation, soil moisture, wind

• Types of Drought (NIDIS):

  • Meteorological: Prolonged dry weather patterns

  • Hydrological: Reduced surface & groundwater supply

  • Agricultural: Crop stress from low soil moisture

  • Socioeconomic: Disruption in supply/demand of goods

  • Ecological: Damage to ecosystems and biodiversity

• Major Impacts:

  • Wildfire: Amazon (2005), CA wildfires (2020-21) —> 1.8 million acres burned

  • Agriculture: 2012 US corn yield lowest in 17 years —> record prices

  • Humanitarian: Hunger, disease, displacement, economic hardship

  • Future hotspots: Interior continents, mid-latitudes (e.g., SW US, Sahel, Mediterranean)

• Drought Severity Index (DSI)

  • Southern Europe faces desertification as rainfall decreases and evaporation rises

  • Drought severity index: positive= wet, negative= dry

  • Index less than or equal to -4 = extreme drought

Hurricane Frequency and Intensity

• Hurricane Katrina (2005):

  • Sparked public attention and debate on climate change

  • Al Gore’s film implied a climate link, generating controversy

  • Stimulated research into hurricane— global warming connections

• Hurricane & Typhoon Activity Influenced By:

  • Complex ocean— atmosphere interactions

  • Atlantic Multidecadal Oscillation (AMO):

    • Cyclical warming of tropical Atlantic boosts hurricane frequency

  • El Niño:

    • Inhibits storm development by generating strong upper-level winds

• Climate Models & Storm Projections:

  • Some predict increased hurricane frequency, but factors are complex

  • Studies suggest hurricane intensity could rise by 2-11% by 2100

• Mechanism Linking Warming to Intensity:

  • Warmer oceans—> more evaporation—> more latent heat released via condensation

  • Latent heat fuels storm growth

  • Link between sea surface temperature & storm intensity is plausible but not yet proven

In summary

• Patterns of precipitation are changing

• Extreme climate events, including extreme heat waves and more intense precipitation events, are more common today that in the past

• It is even possible that elevated sea surface temperatures could lead an increase in the intensity of hurricanes