Taking Earth's Temperature
Narration: Sarah DeWitt
[Narrator] The Earth is a complex system and scientists are continually investigating the intricate workings of our home planet. Part of what makes the Earth so unique is its climate. Many scientists are concerned that Earth's climate is changing at an unprecedented rate. How do scientists study how warm the planet is? Here's a look at the tools NASA scientists use to take Earth's temperature. Models are powerful tools for understanding Earth's complex system. To create a model, scientist must first characterize a system by identifying the processes that govern its evolution. Those processes are represented by equations that are solved on powerful computers. This animation comes from an atmospheric assimilation. It uses observations of temperature, moisture, and wind to provide a picture of Earth's hydrological cycle. Once a model is in place, the resulting simulations must be proven to match real world measurements.
[Michelle Rienecker] Well, models are important for the scientific community because they capture really the essence and basic understanding that we have of how our system works on a lot of different timescales and space scales for a lot of different applications from weather all the way through to climate.
[Narrator] In the 1970's, Dr. James Hansen and colleagues at NASA built a simple climate model to simulate how changes in the atmosphere cause Earth's average temperature to change over time. Hansen's early climate models showed that both human and natural activities could force Earth's climate to change. The model revealed that natural forcings like volcanic eruptions or changes in the sun's activities tend to go up and down over long periods of time. But, human forcings from greenhouse gas emissions are steadily increasing. Hansen's early simulation revealed that human forcings on climate would dominate in the future. But, he needed real world temperature data on a global scale to determine when. The most reliable measurement of global temperature came from weather stations scattered around the globe. Hansen knew that weather fluctuations would cause short-term changes at individual stations, but he reasoned that taking averages over several years and appropriately weighting each stations data would deliver meaningful temperature information A consistent trend of warming is visible in both the global temperature data and the global climate model.
[James Hansen] We have a pretty good understanding now of how sensitive the climate is to the increases in the greenhouse gases. This comes particularly from the history of the Earth. Our climate models give us an answer too, but there are a lot of uncertainties in the climate models.
[Michelle Rienecker] The challenges associated with modeling are manifold. The Earth really acts as system. You know, the ocean interacts with the atmosphere interacts with the land surface, so representing all of this sort of complex system really are a major challenge.
[Narrator] NASA's upcoming Glory mission will measure two key climate forcings: solar irradiance and atmospheric aerosols. These measurements will help to improve the accuracy of global climate models. NASA missions like Glory will help scientists fine-tune their understanding of Earth’s climate providing a more accurate diagnosis of the Earth’s health today and far into the future.