Global Warming FAQ

Answers to a series of global warming frequently asked questions are given below. Special thanks are given to Patrick Brown for preparing this resource. https://patricktbrown.org/

  • How do we know that the world is warming?

    Scientists use data from meteorological stations, ships, buoys and satellites to construct instrumental records of temperature as far back as the late 19th century. These temperature reconstructions show a significant warming of the globe over this time period (figure 1). figure 1 – National Aeronautics and Space Administration (NASA) global surface temperature over the period…

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  • How can there be global warming when last week/month was so cold?

    The local temperature at any given location is mostly determined by changes in the flow of heat around the Earth’s surface. This idea is illustrated in weather maps that represent the movement of cold and warm air with fronts (figure 1). If cooler air moves over a particular location this will generally be cancelled out…

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  • Hasn’t climate changed before?

    Yes. Climate change has occurred many times in the Earth’s 4.5 billion year history due to a variety of causes. Scientists use these past changes in climate to better understand the changes we are currently experiencing. Many of Earth’s previous climate changes were due to factors that changed slowly over long periods of time (tens…

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  • Why do scientists think current climate change is being caused by humans?

    The main reason has to do with the fundamental physics of the greenhouse effect. Greenhouse gasses are transparent to solar radiation but are relatively opaque to terrestrial radiation. This means that greenhouse gasses inhibit the Earth’s ability to radiate energy to space. Therefore, all else being equal, a higher atmospheric concentration of greenhouse gasses should…

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  • How can we project climate change out toward the end of the century when we can’t even predict the weather 2 weeks from now?

    Local weather is the result of somewhat random fluctuations in the flow of the atmosphere around the planet. This makes the weather at any given location difficult to predict past about a week in time. Climate, or average weather, on the other hand, is largely determined by external forcings that are more predictable. This idea…

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  • Weren’t scientists all predicting global cooling in the 1970′s?

    No. From the 1940s to the 1970s, the global surface temperature decreased very slightly. This probably occurred because over that time period the cooling effect from human produced aerosols was slightly larger than the warming effect from human produced greenhouse gasses. A minority of scientists predicted that the cooling effect from increasing aerosols would continue…

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  • Don’t humans produce just a small percentage of the total carbon that is emitted into the atmosphere?

    Carbon is constantly moving between the atmosphere, ocean, land and biosphere (figure 1). Before humans started burning fossil fuels, all this movement of carbon was balanced so that, over the previous few thousand years, there was no net change in the amount of CO2 in the atmosphere. Ever since the industrial revolution, however, the burning of…

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  • Why would a few degrees of warming be a big deal?

    Because we all experience temperature changes of tens of degrees every day, a few degrees of global warming may not seem like a lot. A few degrees of change in the global surface temperature can, however, indicate a drastic change in the Earth’s climate. This can be exemplified by considering climate changes of the past.…

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  • Didn’t “Climate Gate” show that the science of global warming was based on fabricated data?

    “Climate Gate” refers to a situation where the servers of the University of East Anglia were illegally hacked and personal emails from a group of scientists associated with the Climate Research Unit (CRU) were posted online. Thousands of personal emails were published that spanned a time period of over a decade. Out of these thousands…

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