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What is Climatology?

Climatology is the study of Earth’s weather over long enough periods of time to allow for averages and trends to be developed. What that means is that rather than study the immediate weather and what its impact is or will be in the next day or two as meteorologists do, climatologists study long-term trends in the Earth’s weather and try to understand what the impact of various things, including human activity, will be over decades or centuries.

Today, climatologists hold an almost sacred position among atmospheric scientists as humans struggle to understand the implications of global warming. In fact, until the 1970s, climatology was considered by many to be somewhat routine and boring.  With the knowledge that human actions can impact the climate, however, the work of men and women in the field of climatology became paramount in government policy. Today, climatologists are routinely consulted by the Intergovernmental Panel on Climate Change in the United Nations and are among the most well-known scientists to the public.

History and Organization of Climatology

Data on the weather has been kept by humans for several thousand years, but the systematic study of such data and theories about how it might predict long-term trends in weather have only been around for roughly one thousand years. The Chinese were the first to connect observations of ancient plants with predictions about past weather, a field that is today recognized as paleoclimatology.

The practice of systematically studying the weather was pretty much abandoned after Chinese efforts subsided and did not resume again until the late 17th century when Edmund Halley, famous for Halley’s Comet, began keeping track of the trade winds. Though his records were primarily used for travel and navigation, they nonetheless provided valuable clues about the weather and the practice of mapping large weather patterns became of interest to many scientists, including Benjamin Franklin. The value of climate data in economic concerns (ship travel, etc.) was what ultimately led to its wider study and to the funding of climate science, a fact that is still true today.

The early forerunners of climate science would probably not recognize the discipline today. Satellites and super computers have replaced the approach used by Benjamin Franklin to map the Gulf Stream, which was based around stories of whale navigation and collecting complaints from the postal service. He observed that it took several weeks longer to reach New York from England than it did to Reach Rhode Island from England, despite the two being only a few dozen miles apart by land. This observation led him to follow the data for a number of different ships crossing the Atlantic and eventually to the discovery of the Gulf Stream.

Today, climatology is considered a subset of atmospheric physics, which is itself a branch of the physical sciences. Climatology is broken into several major sub-fields. Those fields include, but are not limited to:

  • Dendroclimatology – The specific study of tree rings and how they relate to the climate
  • Dynamic Climatology – The study of large-scale patterns and how they can be used to understand global weather
  • Historical Climatology – The study of climate in relationship to human history using evidence like direct temperature recording, agricultural practices, or indirect historical evidence
  • Paleoclimatology – Reconstruction of past climates using fossil evidence, ice cores, and tree rings
  • Physical Climatology – The study of physical processes such as evaporation, cloud formation, aersol dispersal, and more
  • Tornado Climatology – The study of how long-term trends in climate change can affect the strength, location, and frequency of tornados and thunderstorms.
  • Tropical Cyclone Climatology – The study of how climate change affects the strength, locations, and frequency of tropic storms.

Urban Climatology and Climate Change

The understanding of global warming, or more accurately global climate change, as a result of human actions is a major research area in climatology. There are several specific branches of the science that inform our understanding of how humans are currently impacting the climate, but urban climatology has become a major focus in recent years.

Urban climatology is concerned with how urban growth affects the atmosphere and vice versa. The interest in city weather began in the early 19th century, but it wasn’t until the latter part of the 20th century that the tools for truly understand the effects of large-scale city building on the climate became available.

It has long been known that cities, because of their use of dark asphalt and concrete surfaces, retain heat. It took over a century, however, to begin to understand how that retained heat, now known as the urban heat island (UHI) effect, impacts the weather and climate. Satellite data has been instrumental in the understanding that UHIs can affect local wind patterns, precipitation, cloud cover, fog, and humidity. Probably most profound is the fact that UHIs retain heat and that they lead to more of an increase in nighttime temperatures than daytime temperatures. The result is a lack of cooling during hot summer periods and thus increased use of air conditioning. Of course, air conditioning relies on fossil fuels for electricity generation, so even if the UHI does not directly affect the climate by changing weather patterns, it does lead to massive increases in fossil fuel use and thus increased greenhouse gas output.

Climate Indices and Models

The modern study of climatology, particularly dynamic climatology, relies on the understanding of climate indices. Climate indices are large-scale weather patterns that are consistent and measureable. The goal of an index is to combine a number of factors into a large, generalized description of either air or ocean phenomena that can be used to track the global climate system.

The indices used today include the following, which are discussed in greater detail in other sections:

  • El Nino - Southern Oscillation (ENSO)
  • Interdecadal Pacific Osciallation (IPO)
  • Madden-Julian Oscillation (MJO)
  • North Atlantic Oscillation (NAO)
  • Northern Annular Mode/Arctic Oscillation (NAM/AO)
  • Northern Pacific Index (NPI)
  • Pacific Decadal Oscillation (PDO)

Each index above indicates a single, large-scale conglomeration of related weather patterns that have predictive value for general weather trends. Because of their predictive value, these indices, along with ice cover in the Arctic and Antarctic (and even information gleaned from studying the climates of other planets in the Solar System) are used to construct climate models.

The goal of a climate model is to project future trends in Earth’s weather and climate.  This includes things like overall average temperature, ocean acidity, trends in storm strength and frequency, etc. There are several different categories of climate model as follows:

  • Zero-dimensional Models – These are simple models that take into account the amount of radiation entering and leave the atmosphere. The idea is that the two should be roughly equivalent otherwise the planet’s temperature will change.
  • One-dimensional Models – These take into account everything that a zero-dimensional model does, but also factor in the convective movement of heat through the atmosphere. These models are used to determine how changes in various greenhouse gas concentrations will affect surface temperature. A one-dimensional model is also called a radiative-convective model because it factors in the vertical movement of heat by convection in the atmosphere.
  • Higher-dimensional Models – Adding parameters to a one-dimensional model leads to more complicated models with more predictive power. For instance, factoring in the horizontal movement of energy in the atmosphere or how albedo (reflection of sunlight by ice) affects energy transfer are both ways of increasing the dimensions of a climate model.
  • Global Climate Models – Also called general circulation models, these models take into account the movement of energy in three dimensions as well as over time. Most of these models, despite being around since the late 1960s are considered “under development” and have areas of uncertainty.
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