Synthetic GeoJSON data are created with a quasi-normal spatial distribution and displayed as circle markers on a Leaflet map. The markers are styled using a color ramp that is tied to one numerical property ("year" in this case) and a size scale that is tied to another ("size"). The scatterplot of size vs. year is created using Highcharts and placed in a Leaflet control box.
answer to https://stackoverflow.com/questions/7562095/redirect-on-select-option-in-select-box. code salvaged via wayback machine: http://web.archive.org/web/20130722234047/http://jsfiddle.net:80/davidThomas/raqRG/1/