Month: July 2023

Noticeable spikes before dawn on Wednesday at the CBD and middle suburb sites – in the 490-500 ppm range, and a brief spike of similar magnitude on the city edge, (though in the evening hours and of shorter duration).  The average across sites for the day was 437 ppm, maintaining a higher level from yesterday compared to the previous three days.

Daily Averages – Phase 2 (See explanation of differences between Phase 1 and Phase 2 data)

For reference, latest monthly average (May 2023) from CSIRO for Kennaook/Cape Grim in NW Tasmania was 415.7 ppm. (Note – these are provisional values, subject to revision folllowing sensor re-calibrations and other checks.)

Date	Petrie Terrace	Chapel Hill	Bellbird Park
5-Jul-2023	442 ppm	441 ppm	429 ppm
4-Jul-2023	449 ppm	443 ppm	429 ppm
3-Jul-2023	428 ppm	429 ppm	412 ppm
2-Jul-2023	424 ppm	425 ppm	414 ppm
1-Jul-2023	419 ppm	407 ppm	405 ppm
30-Jun-2023	414 ppm	405 ppm	402 ppm
29-Jun-2023	415 ppm	409 ppm	405 ppm
28-Jun-2023	435 ppm	427 ppm	428 ppm
27-Jun-2023	426 ppm	409 ppm	415 ppm
26-Jun-2023	412 ppm	402 ppm	412 ppm
25-Jun-2023	447 ppm	426 ppm	429 ppm
24-Jun-2023	427 ppm	417 ppm	423 ppm
23-Jun-2023	434 ppm	427 ppm	435 ppm
22-Jun-2023	442 ppm	425 ppm	436 ppm
21-Jun-2023	443 ppm	421 ppm	437 ppm
20-Jun-2023	421 ppm	414 ppm	417 ppm
19-Jun-2023	430 ppm	418 ppm	419 ppm
18-Jun-2023	436 ppm	426 ppm	434 ppm
17-Jun-2023	440 ppm	429 ppm	437 ppm
16-Jun-2023	438 ppm	421 ppm	433 ppm
15-Jun-2023	433 ppm	412 ppm	428 ppm
14-Jun-2023	435 ppm	425 ppm	438 ppm
13-Jun-2023	441 ppm	436 ppm	442 ppm
12-Jun-2023	442 ppm	439 ppm	448ppm
11-Jun-2023	443 ppm	441 ppm	451 ppm
10-Jun-2023	446 ppm	432 ppm	4444 ppm
9-Jun-2023	441 ppm	428 ppm	440ppm

Much higher levels on Tuesday following several days of stronger, predominantly westerly winds.  All three sites averaged above the recent background level measured by CSIRO at Kennaook/Cape Grim from air streaming in from the Southern Ocean.  These differences were +33, +27 and +19 ppm for the CBD (Petrie Terrace), a middle suburb (Chapel Hill), and city edge (Bellbird Park), respectively. The build-up in carbon dioxide concentrations across the day – apparent in the first graph – may have resulted from the much lower wind speeds (9 and 6 km/h at 9 a.m. and 3 p.m. measured at Archerfield), conditions which allow emissions to accumulate.

Daily Averages – Phase 2 (See explanation of differences between Phase 1 and Phase 2 data)

For reference, latest monthly average (May 2023) from CSIRO for Kennaook/Cape Grim in NW Tasmania was 415.7 ppm. (Note – these are provisional values, subject to revision folllowing sensor re-calibrations and other checks.)

Date	Petrie Terrace	Chapel Hill	Bellbird Park
4-Jul-2023	449 ppm	443 ppm	429 ppm
3-Jul-2023	428 ppm	429 ppm	412 ppm
2-Jul-2023	424 ppm	425 ppm	414 ppm
1-Jul-2023	419 ppm	407 ppm	405 ppm
30-Jun-2023	414 ppm	405 ppm	402 ppm
29-Jun-2023	415 ppm	409 ppm	405 ppm
28-Jun-2023	435 ppm	427 ppm	428 ppm
27-Jun-2023	426 ppm	409 ppm	415 ppm
26-Jun-2023	412 ppm	402 ppm	412 ppm
25-Jun-2023	447 ppm	426 ppm	429 ppm
24-Jun-2023	427 ppm	417 ppm	423 ppm
23-Jun-2023	434 ppm	427 ppm	435 ppm
22-Jun-2023	442 ppm	425 ppm	436 ppm
21-Jun-2023	443 ppm	421 ppm	437 ppm
20-Jun-2023	421 ppm	414 ppm	417 ppm
19-Jun-2023	430 ppm	418 ppm	419 ppm
18-Jun-2023	436 ppm	426 ppm	434 ppm
17-Jun-2023	440 ppm	429 ppm	437 ppm
16-Jun-2023	438 ppm	421 ppm	433 ppm
15-Jun-2023	433 ppm	412 ppm	428 ppm
14-Jun-2023	435 ppm	425 ppm	438 ppm
13-Jun-2023	441 ppm	436 ppm	442 ppm
12-Jun-2023	442 ppm	439 ppm	448ppm
11-Jun-2023	443 ppm	441 ppm	451 ppm
10-Jun-2023	446 ppm	432 ppm	4444 ppm
9-Jun-2023	441 ppm	428 ppm	440ppm

With values slightly higher and winds more southerly, a simple test of the hypothesis of an association between Brisbane’s CO2 concentrations and wind direction seemed in order.  Step 1) Calculate the average wind direction from the BOM’s 9am and 3am reports as recorded at Archerfield for each of the last 25 days. Step 2) Calculate the absolute difference between 270 degrees and each of these values.  If zero, this number indicates winds from the west, if higher it indicates directions increasingly further away from the west.  Step 3), calculate the Pearson correlation between the daily average concentration across our three sensor sites and this value for those 25 days.  The result? r = 0.454, p= 0.02.  The tentative interpretation of this outcome – very unlikely to be due to chance? Winds from the west tend to bring air with lower carbon dioxide concentrations, winds from other directions tend to bring air across the city, with higher concentrations.  This isn’t just because two of our three sensors are towards the west – it’s also that the population distribution of Brisbane leaves a relatively less populated notch towards the west, meaning there is “less city” between even the CBD and the western urban edge than for other directions. A limitation of this analysis is that wind speed isn’t taken into account, and this could exert its own effect by simply pushing anthropogenic emissions out of the city and diluting the concentrations, irrespective of direction.  With more data, this factor can also be examined.

Daily Averages – Phase 2 (See explanation of differences between Phase 1 and Phase 2 data)

For reference, latest monthly average (May 2023) from CSIRO for Kennaook/Cape Grim in NW Tasmania was 415.7 ppm. (Note – these are provisional values, subject to revision folllowing sensor re-calibrations and other checks.)

Date	Petrie Terrace	Chapel Hill	Bellbird Park
3-Jul-2023	428 ppm	429 ppm	412 ppm
2-Jul-2023	424 ppm	425 ppm	414 ppm
1-Jul-2023	419 ppm	407 ppm	405 ppm
30-Jun-2023	414 ppm	405 ppm	402 ppm
29-Jun-2023	415 ppm	409 ppm	405 ppm
28-Jun-2023	435 ppm	427 ppm	428 ppm
27-Jun-2023	426 ppm	409 ppm	415 ppm
26-Jun-2023	412 ppm	402 ppm	412 ppm
25-Jun-2023	447 ppm	426 ppm	429 ppm
24-Jun-2023	427 ppm	417 ppm	423 ppm
23-Jun-2023	434 ppm	427 ppm	435 ppm
22-Jun-2023	442 ppm	425 ppm	436 ppm
21-Jun-2023	443 ppm	421 ppm	437 ppm
20-Jun-2023	421 ppm	414 ppm	417 ppm
19-Jun-2023	430 ppm	418 ppm	419 ppm
18-Jun-2023	436 ppm	426 ppm	434 ppm
17-Jun-2023	440 ppm	429 ppm	437 ppm
16-Jun-2023	438 ppm	421 ppm	433 ppm
15-Jun-2023	433 ppm	412 ppm	428 ppm
14-Jun-2023	435 ppm	425 ppm	438 ppm
13-Jun-2023	441 ppm	436 ppm	442 ppm
12-Jun-2023	442 ppm	439 ppm	448ppm
11-Jun-2023	443 ppm	441 ppm	451 ppm
10-Jun-2023	446 ppm	432 ppm	4444 ppm
9-Jun-2023	441 ppm	428 ppm	440ppm

Carbon dioxide concentrations rose somewhat on Saturday, perhaps due to the afternoon winds picking up and changing direction to come from the S.E. (20 km/hr at 3 p.m. recorded at Archerfield). This marks a change from three days of strong westerlies moving volumes of non-urban air across the city.  South-easterlies would bring air across the city towards the monitors, tending to pick up the city’s anthropogenic emissions en route. A rise later in the day was largely confined to the Chapel Hill site, however, so the story is probably more complex (as is normal for data of this type).

Daily Averages – Phase 2 (See explanation of differences between Phase 1 and Phase 2 data)

For reference, latest monthly average (May 2023) from CSIRO for Kennaook/Cape Grim in NW Tasmania was 415.7 ppm. (Note – these are provisional values, subject to revision folllowing sensor re-calibrations and other checks.)

Date	Petrie Terrace	Chapel Hill	Bellbird Park
2-Jul-2023	424 ppm	425 ppm	414 ppm
1-Jul-2023	419 ppm	407 ppm	405 ppm
30-Jun-2023	414 ppm	405 ppm	402 ppm
29-Jun-2023	415 ppm	409 ppm	405 ppm
28-Jun-2023	435 ppm	427 ppm	428 ppm
27-Jun-2023	426 ppm	409 ppm	415 ppm
26-Jun-2023	412 ppm	402 ppm	412 ppm
25-Jun-2023	447 ppm	426 ppm	429 ppm
24-Jun-2023	427 ppm	417 ppm	423 ppm
23-Jun-2023	434 ppm	427 ppm	435 ppm
22-Jun-2023	442 ppm	425 ppm	436 ppm
21-Jun-2023	443 ppm	421 ppm	437 ppm
20-Jun-2023	421 ppm	414 ppm	417 ppm
19-Jun-2023	430 ppm	418 ppm	419 ppm
18-Jun-2023	436 ppm	426 ppm	434 ppm
17-Jun-2023	440 ppm	429 ppm	437 ppm
16-Jun-2023	438 ppm	421 ppm	433 ppm
15-Jun-2023	433 ppm	412 ppm	428 ppm
14-Jun-2023	435 ppm	425 ppm	438 ppm
13-Jun-2023	441 ppm	436 ppm	442 ppm
12-Jun-2023	442 ppm	439 ppm	448ppm
11-Jun-2023	443 ppm	441 ppm	451 ppm
10-Jun-2023	446 ppm	432 ppm	4444 ppm
9-Jun-2023	441 ppm	428 ppm	440ppm

Slightly weaker winds on Friday but still predominantly from the west (19 km/hr – WSW and 14 km/h – WNW at 9 a.m. and 3 p.m. recorded at Archerfield). Consequently carbon dioxide concentrations remained at their recent ‘lows’.   (To reinforce yesterday’s point that these ‘lows’ are a great deal higher than pre-industrial levels, it’s worth remembering that the value of 410 ppm – the average we recorded in Brisbane for yesterday – had never been recorded as the monthly average background level at Kennaook/Cape Grim before July 2020, and the very lowest value we recorded at the bottom of the diurnal cycle yesterday (393 ppm at Bellbird Park at 1:30 pm) had never been recorded as the monthly average there until May 2013.  Even the ‘lows’ are high.

Daily Averages – Phase 2 (See explanation of differences between Phase 1 and Phase 2 data)

For reference, latest monthly average (May 2023) from CSIRO for Kennaook/Cape Grim in NW Tasmania was 415.7 ppm. (Note – these are provisional values, subject to revision folllowing sensor re-calibrations and other checks.)

Date	Petrie Terrace	Chapel Hill	Bellbird Park
1-Jul-2023	419 ppm	407 ppm	405 ppm
30-Jun-2023	414 ppm	405 ppm	402 ppm
29-Jun-2023	415 ppm	409 ppm	405 ppm
28-Jun-2023	435 ppm	427 ppm	428 ppm
27-Jun-2023	426 ppm	409 ppm	415 ppm
26-Jun-2023	412 ppm	402 ppm	412 ppm
25-Jun-2023	447 ppm	426 ppm	429 ppm
24-Jun-2023	427 ppm	417 ppm	423 ppm
23-Jun-2023	434 ppm	427 ppm	435 ppm
22-Jun-2023	442 ppm	425 ppm	436 ppm
21-Jun-2023	443 ppm	421 ppm	437 ppm
20-Jun-2023	421 ppm	414 ppm	417 ppm
19-Jun-2023	430 ppm	418 ppm	419 ppm
18-Jun-2023	436 ppm	426 ppm	434 ppm
17-Jun-2023	440 ppm	429 ppm	437 ppm
16-Jun-2023	438 ppm	421 ppm	433 ppm
15-Jun-2023	433 ppm	412 ppm	428 ppm
14-Jun-2023	435 ppm	425 ppm	438 ppm
13-Jun-2023	441 ppm	436 ppm	442 ppm
12-Jun-2023	442 ppm	439 ppm	448ppm
11-Jun-2023	443 ppm	441 ppm	451 ppm
10-Jun-2023	446 ppm	432 ppm	4444 ppm
9-Jun-2023	441 ppm	428 ppm	440ppm