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Temperature trends and UV in 2040 at Ispra and Rome

To study the possible effect of atmospheric changes on UV radiation (UV irradiance variations), the same methodology applied to the ozone series is used to analyse the surface temperature trends at Rome and Ispra. The analysis on the time series of monthly values in the period 1958-1998 at Ispra and 1926-1997 at Rome shows the existence of trends only if the detected change points are not considered.

The effect of the observed cooling of the stratosphere is considered referring to the latest published trends (WMO, 1999) to the levels between 100hPa and 1hPa.

The STAR model (Ruggaber et al., 1994) is used to derive the 305 nm UV irradiance, the integrated 290-325 nm irradiance and the erythemally weighted irradiance in the year 2040 under five different hypotesis:

1A: ozone decrease following a linear extrapolation from year 2000 to 2040, based on Table 3 results;

1B: ozone decrease as described in 1A coupled with the surface monthly temperature increase linearly extrapolated;

2A: ozone decrease following a linear extrapolation from year 2000 to 2040, based on Table 4 results;

2B: ozone decrease as described in 2A and surface temperature increase as in 1B;

2C: the same as in 2B coupled with the stratospheric temperature decrease as reported in the last ozone assessment (WMO, 1999).

Results for 1A-1B and 2A-2B-2C hypothesis are reported in Table 5 and Table 6 respectively. The uncertainties of the model (17% - Schwander et al., 1997) allow to detect only the 305 nm irradiance increases for 1A and 1B. Hypotesis 2A, 2B and 2C lead to a more significant increase in the integrated and erythemally weighted irradiance and the results are shown in Table 7 for 2C case. The significance level is there lowered to 14%.

Table 5. Mean monthly percentage differences of O3 and UV radiation at 305 nm between 1999 and 2040 due to a linear decrease in ozone. Calculations are performed with and without surface temperature forcing (1A and 1B hypothesis, see text). No significant differences exist in the output. Blank cells indicate absence of trend; significant trends (>17%, as obtained from Schwander et al., 1997) are in bold.

 
ROME

 

ISPRA

Month

(%)

Irradiance

305 nm

(%)

Ozone

(%)

Irradiance

305 nm

(%)

Ozone

Jan
+21.3
-6.0
+16.4
-4.9
Feb
+39.1
-11.4
+9.0
-3.6
Mar
   
+10.3
-4.8
Apr
   
+3.9
-2.9
May
+11.1
-6.1
+4.6
-3.6
June
       
July
       
Aug
       
Sept
       
Oct
   
+1.3
-1.8
Nov
+17.0
-6.1
+6.0
-2.8
Dec
+40.5
-10.8
+13.6
-4.3

 

Table 6. Mean monthly percentage differences in 305 nm UV and ozone without and with temperature forcing. Change points are included as in conditions 2A, 2B and 2C (see text). Blank cells indicate absence of trend; significant trends (>17%, as obtained from Schwander et al., 1997) are in bold.

 
ROME

 

ISPRA

Month

(%)

Irradiance

305 nm

(%)

Ozone

(%)

Surface Temp

(%)

Irradiance

305 nm

(%)

Ozone

(%)

Surface Temp

 
2A
2B
2C
   
2A
2B
2C
   
Jan
 
-1.1
+1.8
 
+1.8
 
-3.3
-0.2
 
+18.2
Feb
 
-1.1
+1.3
 
+1.2
+141
+141
+145
-27.3
 
Mar
   
+0.9
   
+85.5
+85.5
+88.3
-23.7
 
Apr
   
+0.6
       
-0.9
   
May
 
-1.0
+0.6
 
+0.4
+42.5
+42.5
+44.5
-18.5
 
June
+35.5
+35.5
+37.2
-17.7
     
-1.0
   
July
 
-1.0
+0.6
 
+0.4
 
-2.8
-1.0
 
+1.9
Aug
+12.9
+12.9
+14.6
-7.6
+0.4
 
-2.9
-1.2
 
+2.8
Sept
   
+0.7
       
-1.3
   
Oct
   
+0.9
       
-1.3
   
Nov
   
+1.3
       
-0.3
   
Dec
   
+1.8
     
-3.0
<0.01
 
+10.4

 

Table 7. Mean monthly percentage differences in integrated not weighted UV and integrated erythemally weighted UV after running under 2C hypothesis (see text). Ozone decrease is evaluated at the right of the change point. Blank cells indicate absence of trend; significant trends (>14%, as obtained from Schwander et al., 1997) are in bold.

 
ROME

 

ISPRA

month

%

integrated irradiance

% Ozone

%

Surface

Temp

%

integrated irradiance

% Ozone

%

Surface

Temp

Not weighted

Erythem.

Weighted

Not weighted

Erythem.

Weighted

Jan
-0.3
+0.2
 
+1.8
-2.8
-2.1
 
+18.2
Feb
-0.4
+0.1
 
+1.2
+17.1
+56.3
-27.3
 
Mar
-0.5
+0.0
   
+12.1
+44.0
-23.7
 
Apr
-0.5
-0.0
   
-2.7
-1.7
   
May
-0.5
+0.1
 
+0.4
+7.7
+30.8
-18.5
 
June
+8.6
+30.5
-17.7
 
-2.4
-1.6
   
July
-0.4
+0.2
 
+0.4
-2.4
-1.6
 
+1.9
Aug
+3.3
+11.7
-7.6
+0.4
-2.5
-1.7
 
+2.8
Sept
-0.5
+0.1
   
-2.8
-2.0
   
Oct
-0.5
+0.1
   
-3.0
-2.3
   
Nov
-0.4
+0.1
   
-3.0
-2.4
   
Dec
-0.4
+0.3
   
-2.7
-2.0
 
+10.4

 

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