Table 1.
Differences of mean pollen indices between periods of 2001–2010 and 1994–2000 in the contiguous US. 95% confidence intervals are included in the parentheses.
| Start Date (Days) | Season Length (Days) | Peak Value a (%) | Annual Production a (%) | # of stations | |
|---|---|---|---|---|---|
| Birch | −2.3 (−7.0, 1.9) | −4.4* (−8.8, −0.6) | +44.9* (7.9, 82.0) | +42.8* (4.6, 81.1) | 19 |
| Oak | −4.4* (−7.4, −1.5) | −3.1 (−7.0, 0.8) | +86.4* (37.9, 134.8) | +92.5* (29.4, 155.7) | 28 |
| Ragweed | −4.0 (−7.6, −0.4) | +1.3 (−1.1, 3.6) | +12.4 (−22.9, 47.7) | −3.1 (−30.0, 23.8) | 20 |
| Mugwort | −12.5 (−145.9, 120.9) | +10 (−66.2, 86.2) | −45.4 (−127.4, 36.5) | −51.5 (−179.0, 76.1) | 2 |
| Grass | −0.2 (−4.7, 4.3) | −4.8 (−13.7, 4.2) | +23.0 (−15.0, 61.0) | 43.4 (−3.4, 90.3) | 26 |
| Average | −3.0* (−4.9,−1.1) | −2.6 (−5.4, 0.2) | +42.4* (21.9, 62.9) | +46.0* (21.5, 70.5) | 31 |
a
The relative change in peak value was calculated by dividing the changes in mean peak value from two periods by the mean peak value in the period of 1994–2000 (i.e., ), and likewise for annual production.
b
The changes in a mean pollen index for a given taxa during two periods at all available stations were used to calculate the nationwide average and the 95% confidence intervals.
Asterisk (*) indicates statistically significant difference at 5% level based on Student’s t test and Benjamini-Hochber control procedure (false discovery rate < 5%).