Please see here for details about the calibration improvements made since Phase 2. The lowest overall daily average in Phase 3 data so far on Saturday – 431 ppm, but still some 14 ppm above the latest monthly mean (for August) from the CSIRO’s Cape Grim/Kennaook station. Observations of daily carbon dioxide cycles are can be found in the literature going back at least seventy years. Today’s second chart shows measurements made over a corn-field in Iowa in the summer of 1952. The solid line shows data from a few meters above the field, and the dashed line 152m avove it. The “Normal” reference line of 0.594 mg/l corresponds to 300 ppm.
Daily Averages – Phase 3
For reference, the latest full month of ‘clean air’ sampled by CSIRO at Cape Grim/Kennaook (August) has a mean value of 417.1 ppm
| Date | Petrie Terrace | Chapel Hill | Bellbird Park |
| 09-12-2023 | 420 ppm | 436 ppm | 426 ppm |
| 08-12-2023 | 430ppm | 437 ppm | 438 ppm |
| 07-12-2023 | 431 ppm | 439 ppm | 438ppm |
| 06-12-2023 | 427 ppm | 436 ppm | 436 ppm |
| 05-12-2023 | 426 ppm | 433 ppm | 428 ppm |
| 04-12-2023 | 435 ppm | 445 ppm | 439 ppm |
| 03-12-2023 | 438 ppm | 453 ppm | 465 ppm |
| 02-12-2023 | 434ppm | 443 ppm | 442 ppm |
| 01-12-2023 | 444 ppm | 451 ppm | 459 ppm |
| 30-11-2023 | 447ppm | 464 ppm | 457 ppm |
| 29-11-2023 | 437 ppm | 437 ppm | 436 ppm |
| 28-Nov-2023 | 444 ppm | 448 ppm | 448 ppm |
| 27-Nov-2023 | 433 ppm | 436 ppm | 444 ppm |
| 26-Nov-2023 | 427 ppm | 435 ppm | 447 ppm |
| 25-Nov-2023 | 425 ppm | 430 ppm | 423 ppm |
| 24-Nov-2023 | 429 ppm | 442 ppm | 427 ppm |
| 23-Nov-2023 | 431 ppm | 442 ppm | 432 ppm |
| 22-Nov-2023 | 435 ppm | 437 ppm | 433 ppm |
| 21-Nov-2023 | 440 ppm | 436 ppm | 432 ppm |
Daily Averages – Phase 2 (See explanation of differences between Phase 1 and Phase 2 data)
For reference, latest monthly average (July 2023) from CSIRO for Kennaook/Cape Grim in NW Tasmania was 416.6 ppm. (Note – these are provisional values, subject to revision folllowing sensor re-calibrations and other checks.)
| Date | Petrie Terrace | Chapel Hill | Bellbird Park |
| 19-Aug-2023 | — | 396 ppm | 398 ppm |
| 18-Aug-2023 | 421 ppm | 417 ppm | 418 ppm |
| 17-Aug-2023 | 436 ppm | 425 ppm | 426 ppm |
| 16-Aug-2023 | — | 421 ppm | 420 ppm |
| 15-Aug-2023 | — | 426 ppm | 419 ppm |
| 14-Aug-2023 | 436 ppm | 430 ppm | 430 ppm |
| 13-Aug-2023 | 438 ppm | 428 ppm | 423 ppm |
| 12-Aug-2023 | 436 ppm | 426 ppm | 433 ppm |
| 11-Aug-2023 | 438 ppm | 427 ppm | 430 ppm |
| 10-Aug-2023 | 437 ppm | 427 ppm | 430 ppm |
| 09-Aug-2023 | 431 ppm | 427 ppm | 433 ppm |
| 08-Aug-2023 | 427 ppm | 428 ppm | 436 ppm |
| 07-Aug-2023 | 431 ppm | 427 ppm | 432 ppm |
| 06-Aug-2023 | 431 ppm | 431 ppm | 433 ppm |
| 05-Aug-2023 | 432ppm | 431 ppm | 434 ppm |
| 04-Aug-2023 | 436 ppm | 433 ppm | 435 ppm |
| 03-Aug-2023 | 434 ppm | 432 ppm | 423 ppm |
| 02-Aug-2023 | 432 ppm | 433 ppm | 415 ppm |
| 01-Aug-2023 | 440 ppm | 436 ppm | 431 ppm |
| 31-Jul-2023 | 443 ppm | 431 ppm | 430ppm |
| 30-Jul-2023 | 433 ppm | 424 ppm | 430 ppm |
| 29-Jul-2023 | 434 ppm | 424 ppm | 431 ppm |
| 28-Jul-2023 | 431 ppm | 424 ppm | 426 ppm |
| 27-Jul-2023 | 429 ppm | 430 ppm | 433 ppm |
| 26-Jul-2023 | 432 ppm | 431 ppm | 430 ppm |
| 25-Jul-2023 | 427 ppm | 425 ppm | 424 ppm |
| 24-Jul-2023 | 420 ppm | 418 ppm | 418 ppm |
| 23-Jul-2023 | 424 ppm | 421 ppm | 420 ppm |
| 22-Jul-2023 | 434 ppm | 429 ppm | 428 ppm |
| 21-Jul-2023 | 446 ppm | 430 ppm | — |
| 20-Jul-2023 | 433 ppm | 430 ppm | — |
| 19-Jul-2023 | 437 ppm | 436 ppm | 439 ppm |
| 18-Jul-2023 | 443 ppm | 432ppm | 433 ppm |
| 17-Jul-2023 | 435 ppm | 432 ppm | 436 ppm |
| 16-Jul-2023 | 436 ppm | 432 ppm | 441 ppm |
| 15-Jul-2023 | 449 ppm | 434 ppm | 452 ppm |
| 14-Jul-2023 | 452 ppm | 435 ppm | 448 ppm |
| 13-Jul-2023 | 433 ppm | 431 ppm | 429 ppm |
| 12-Jul-2023 | 437 ppm | 437 ppm | 438 ppm |
| 11-Jul-2023 | 448 ppm | 434 ppm | 438 ppm |
| 10-Jul-2023 | 439 ppm | 424 ppm | 432 ppm |
| 9-Jul-2023 | 423 ppm | 411 ppm | 417 ppm |
| 8-Jul-2023 | 418 ppm | 411 ppm | 414 ppm |
| 7-Jul-2023 | 413 ppm | 407 ppm | 408 ppm |
| 6-Jul-2023 | 434 ppm | 427 ppm | 428 ppm |
| 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 | 444 ppm |
| 9-Jun-2023 | 441 ppm | 428 ppm | 440ppm |