Table 1.
Change in length (day of year, days) of ragweed pollen season as a function of latitude for National Allergy Bureau and Aerobiology Research Laboratories sites along a south–north latitudinal gradient
| Start |
End |
Start |
End |
||||
| Location | Latitude | Years of data | 1995 | 2009 | Change | ||
| Georgetown, TX | 30.63°N | 17 | 198 ± 7 | 320 ± 7 | 195 ± 7 | 313 ± 7 | −4 d |
| Oklahoma City, OK | 35.47°N | 19 | 212 ± 7 | 300 ± 10 | 227 ± 9 | 316 ± 15 | +1 d |
| Rogers, AR | 36.33°N | 15 | 231 ± 7 | 295 ± 8 | 227 ± 6 | 296 ± 8 | −3 d |
| Papillion, NE | 41.15°N | 21 | 212 ± 3 | 281 ± 6 | 208 ± 4 | 288 ± 10 | +11 d |
| Madison, WI | 43.00°N | 27 | 208 ± 2 | 272 ± 4 | 205 ± 3 | 281 ± 6 | +12 d |
| LaCrosse, WI | 43.80°N | 22 | 213 ± 3 | 271 ± 3 | 205 ± 5 | 276 ± 5 | +13 d* |
| Minneapolis, MN | 45.00°N | 19 | 208 ± 5 | 270 ± 6 | 206 ± 7 | 284 ± 7 | +16 d* |
| Fargo, ND | 46.88°N | 15 | 216 ± 4 | 252 ± 8 | 217 ± 4 | 269 ± 8 | +16 d* |
| Winnipeg, MB, Canada | 50.07°N | 16 | 207 ± 7 | 264 ± 6 | 197 ± 7 | 279 ± 7 | +25 d* |
| Saskatoon, SK, Canada | 52.07°N | 16 | 206 ± 12 | 250 ± 6 | 197 ± 13 | 268 ± 7 | +27 d* |
Years represent the number of years for which pollen data were available. Regression analysis was used to determine the “best-fit” line for all years for a given location. This analysis was then used to determine the start and end day of each year (±95% confidence interval) for the duration of the ragweed pollen season in 1995 and again in 2009.
*Significant increase in the length (days) of the ragweed pollen season.