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← Is the weather actually becoming more extreme? - R. Saravanan

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Showing Revision 5 created 08/26/2020 by lauren mcalpine .

  1. From 2016 to 2019,
  2. meteorologists saw record-breaking
    heat waves around the globe,
  3. rampant wildfires
    in California and Australia,
  4. and the longest run
    of category 5 tropical cyclones on record.
  5. The number of extreme weather events
    has been increasing for the last 40 years,
  6. and current predictions suggest
    that trend will continue.
  7. But are these natural disasters
    simply bad weather?
  8. Or are they due to our changing climate?
  9. To answer this question
  10. we need to understand the differences
    between weather and climate—
  11. what they are, how we predict them,
    and what those predictions can tell us.
  12. Meteorologists define weather
    as the conditions of the atmosphere

  13. at a particular time and place.
  14. Currently, researchers can predict
    a region’s weather for the next week
  15. with roughly 80% accuracy.
  16. Climate describes a region’s
    average atmospheric conditions
  17. over periods of a month or more.
  18. Climate predictions can forecast
    average temperatures for decades to come,
  19. but they can’t tell us what specific
    weather events to expect.
  20. These two types of predictions
    give us such different information

  21. because they’re based on different data.
  22. To forecast weather,

  23. meteorologists need to measure
    the atmosphere’s initial conditions.
  24. These are the current levels
    of precipitation, air pressure, humidity,
  25. wind speed and wind direction
    that determine a region’s weather.
  26. Twice every day, meteorologists
    from over 800 stations around the globe
  27. release balloons into the atmosphere.
  28. These balloons carry instruments
    called radiosondes,
  29. which measure initial conditions
  30. and transmit their findings
    to international weather centers.
  31. Meteorologists then run the data
    through predictive physics models
  32. that generate the final weather forecast.
  33. Unfortunately, there’s something stopping
    this global web of data

  34. from producing a perfect prediction:
  35. weather is a fundamentally
    chaotic system.
  36. This means it’s incredibly sensitive
    and impossible to perfectly forecast
  37. without absolute knowledge
    of all the system’s elements.
  38. In a period of just ten days,
  39. even incredibly small disturbances can
    massively impact atmospheric conditions—
  40. making it impossible to reliably
    predict weather beyond two weeks.
  41. Climate prediction, on the other hand,
    is far less turbulent.

  42. This is partly because a region’s climate
    is, by definition,
  43. the average of all its weather data.
  44. But also because climate forecasts ignore
  45. what’s currently happening
    in the atmosphere,
  46. and focus on the range
    of what could happen.
  47. These parameters are known
    as boundary conditions,
  48. and as their name suggests, they act
    as constraints on climate and weather.
  49. One example of a boundary condition
    is solar radiation.

  50. By analyzing the precise distance
    and angle between a location and the sun,
  51. we can determine the amount of heat
    that area will receive.
  52. And since we know how the sun
    behaves throughout the year,
  53. we can accurately predict
    its effects on temperature.
  54. Averaged across years of data,
  55. this reveals periodic patterns,
    including seasons.
  56. Most boundary conditions have well-defined
    values that change slowly, if at all.

  57. This allows researchers to reliably
    predict climate years into the future.
  58. But here’s where it gets tricky.
  59. Even the slightest change
    in these boundary conditions
  60. represents a much larger shift
    for the chaotic weather system.
  61. For example, Earth’s surface temperature
    has warmed by almost 1 degree Celsius
  62. over the last 150 years.
  63. This might seem like a minor shift,
  64. but this 1-degree change
    has added the energy equivalent
  65. of roughly one million
    nuclear warheads into the atmosphere.
  66. This massive surge of energy
    has already led to a dramatic increase
  67. in the number of heatwaves,
    droughts, and storm surges.
  68. So, is the increase in extreme weather
    due to random chance, or changing climate?

  69. The answer is that—
  70. while weather will always
    be a chaotic system—
  71. shifts in our climate do increase
    the likelihood of extreme weather events.
  72. Scientists are in near universal agreement
    that our climate is changing

  73. and that human activity
    is accelerating those changes.
  74. But fortunately,
  75. we can identify what human behaviors
    are impacting the climate most
  76. by tracking which boundary conditions
    are shifting.
  77. So even though next month’s weather
    might always be a mystery,
  78. we can work together to protect
    the climate for centuries to come.