 heat waves. They wreak havoc on our planet, causing fires, agricultural loss, and suffering for hundreds of thousands of lives. We can study these heat waves with a field related to climate modeling called reanalysis. In essence, when a climate model is run, it's initialized with observation data beginning in 1980, and then adjusted to new observations every six hours from that date. When the reanalysis completes, it is filled in the sparse observational record to produce a global gridded data set that represents the climate. Using the reanalysis, we investigate in detail the frequency and intensity of heat waves in the recent past. This allows us to enhance the models, which improves our ability to predict future trends. In this exposition, we'll be using the latest data from NASA's modern air reanalysis for research and applications, also known as MARA II, where we will examine the June, July, and August heat waves from 1980 to 2014 as they occurred in the Northern Hemisphere. This plot displays a 35-year span and illustrates how much warmer or colder the temperature was in each month than the average, from 1980 to 2014. This is called the Departure from the Mean, or Anomaly. Here we can see a shift to a pattern of warmer temperatures and extremes. This pattern was also noted in a recent paper by NASA scientists in 2014. However, this plot still doesn't tell us which locations on the planet the temperatures were above or below average. Using a new three-dimensional visualization tool developed at NASA Goddard, heat waves in the Northern Hemisphere are more easily detected. In this view, we can see the average June, July, August departure from the mean. The year being displayed is shown at the top, and as the map moves upwards, we move forward in time, warmer than average temperatures in red and colder than average temperatures in blue. The color bar shows that the temperature departure ranges from minus 5 to plus 5 Celsius, 9 degrees Fahrenheit, above and below normal. Now, if we turn on the east-west plane, we can see a slice around the earth over 35 years. As we move the plane from north to south, we see the warm temperature departures in red and cold departures in blue. As the plane moves towards the U.S.-Canadian border, we see an increase occurrence of the red color, indicating warmer than average Northern Hemisphere summer temperatures. These intense red colors indicate a heat wave. Now, if we move the z-plane slider up to coincide with the deep red colors, we can see when the heat wave occurred. For instance, in 1980, we see a heat wave in the Midwestern U.S. Later, we see the more recent 2003 European heat wave, then the fierce 2010 Russian heat wave, and finally the 2011 Texas heat wave. We can examine these regions in more detail. Here, we select the continental U.S. and Southern Canada. Again, as the z-plane moves through time, we see heat wave occurrences in 1980, 1988, and 2006. As we take a north-south slice and move it west to east, we see a particularly warm period. This is the 2011 Texas heat wave. This heat wave was the most intense ever recorded, and because it followed a dry winter, its effect on agriculture was exacerbated, and 1.5 million hectares burned. Similarly, if we isolate Eurasia, we can see the harsh 2003 European heat wave, where 70,000 people lost their lives. As we advance in time, we now see the very intense 2010 Russian heat wave that was responsible for crop failures, numerous fires, and 56,000 deaths. The 2010 heat wave was the most severe in this region since the year 1090. Although the three-month average shown here was on the order of 5.8 degrees Celsius above the 35-year average, there were days that were 13 degrees Celsius above normal. We've seen how this visualization tool allows us to examine the space and time extent of heat waves using a reanalysis. By advancing these tools, we are able to further explore the atmospheric mechanisms responsible for these potentially catastrophic weather events.