The reduced albedo, an effort which had never been very vigorously pursued, had added some 2 degrees. The two hundred or so nuclear reactors scattered around the planet had added another 1.5 degrees.

Then Borazjani came to the cocktail of greenhouse gases; but instead of using the 12°K figure from Simmon’s poster, he estimated it was 14°K, and cited a twenty-year-old paper by J. Watkins to support his assertion. Sax had spotted Berkina sitting in the back row near him, and now he sidled over and leaned down until his mouth was by Berkina’s ear, and whispered, “Why isn’t he using Simmon’s work?”

Berkina grinned and whispered back, “A few years ago Simmon published a paper in which he had taken a very complex figure of the UV-halocarbon interaction from Borazjani. He modified it slightly, and that first time he attributed it to Borazjani, but after that when he used it he only cited his own earlier paper. It’s made Borazjani furious, and he thinks Simmon’s papers on this subject are derivative of Watkins anyway, so whenever he talks about warming he goes back to the Watkins work, and pretends Simmon’s stuff doesn’t exist.”

“Ah,” Sax said. He straightened up, smiling despite himself at Borazjani’s subtle but telling little payback. And in fact Simmon was there across the room, frowning heavily.

By now Borazjani had moved on to the warming effects of the water vapor and CO₂ that had been released into the atmosphere, which he estimated together as adding another 10°K. “Some of this might be called a synergistic effect,” he said, “as the desorption of CO₂ is mainly a result of other warming. But other than that I don’t think we can say that synergy has been much of a factor. The sum of the warming created by all the individual methods matches pretty closely the temperatures reported by weather reports from around the planet.”

The video screen displayed his final table, and Sax made a simplified copy of it into his lectern:

From Borazjani 2 February 14, 2102:

Halocarbons: 14

H₂O and CO₂: 10

Moholes: 5

Pre-Soletta Mirrors: 5

Reduced Albedo: 2

Nuclear Reactors: 1.5

Borazjani had not even included the windmill heaters, so on his lectern Sax did. Altogether it came to 37.55°K, a very respectable step, Sax thought, toward their goal of ’53°+. They had only been going at it for sixty years, and already most summer days were reaching temperatures above freezing, allowing arctic and alpine plant life to flourish, as he had seen in the Arena Glacier area. And all this before the introduction of the soletta, which was raising insolation by twenty percent.

The question period had begun, and someone brought up the soletta, asking Borazjani if he thought it was necessary, given the progress being made with the other methods.

Borazjani shrugged in just the way Sax would have. “What does necessary mean?” he replied. “It depends how warm you want it. According to the standard model as initiated by Russell at Echus Overlook, it is important to keep CO₂ levels as low as possible. If we do this, then other warming methods are going to have to be applied to compensate for the loss of the heat that CO₂ would have contributed. The soletta might be thought of as compensating for the eventual reduction of CO₂ to breathable levels.”

Sax was nodding despite himself.

Someone else rose and said, “Don’t you think the standard model is inadequate, given the amount of nitrogen we now know we have?”

“Not if all the nitrogen is put into the atmosphere.”

But this was an unlikely achievement, as the questioner was quick to point out. A fair percentage of the total would remain in the ground, and in fact was needed there for plants. So they were short on nitrogen, as Sax had always known. And if they kept the amount of CO₂ in the air to the lowest levels possible, that left the percentage of oxygen in the air at a dangerously high level, because of its flammability. Another person rose to state that it was-possible that the lack of nitrogen could be compensated for by the release of other inert gases, chiefly argon. Sax pursed his lips; he had been introducing argon into the atmosphere since 2042, as he had seen this problem coming, and there were significant amounts of argon in the regolith. But they were not easy to free, as his engineers had found, and as other people were now pointing out. No, the balance of gases in the atmosphere was turning out to be a real problem.

A woman rose to note that a consortium of transnats coordinated by Armscor was building a continuous shuttle system to harvest nitrogen from the almost pure nitrogen atmosphere of Titan, liquefying it and flying it back to Mars and dumping it in the upper atmosphere. Sax squinted at this, and did some quick calculations on his lectern. His eyebrows shot up when he saw the result. It would take a very great number of shuttle trips to accomplish anything that way, that or else extremely large shuttles. It was remarkable that anyone had thought it worth the investment.

Now they were discussing the soletta again. It certainly had the capability of compensating for the 5 or 8°K that would be lost if they scrubbed the current amount of CO₂ from the air, and probably it would add even more heat than that; theoretically, Sax calculated on his lectern, it could add as much as 22°K. The scrubbing itself would not be easy, someone pointed out. A man standing near Sax, from a Subarashii lab, rose to announce that a demonstration talk on the soletta and the aerial lens would occur later in the conference, when some of these issues would be greatly clarified. He added before sitting down that serious flaws in the single-phase model made the creation of a two-phase model nearly mandatory.

People rolled their eyes at this, and Borazjani declared that the next meeting in the room needed to begin. No one had commented on his skillful modeling, which had sorted out so plausibly all the contributions of the various warming methods. But in a way this was a sign of respect-no one had challenged the model either, Borazjani’s preeminence in this area being taken for granted. Now people stood, and some went up to talk with him; a thousand conversations broke out as the rest filed out of the room and into the halls.

Sax went to lunch with Berkina, in a cafe just outside the foot of Branch Mesa. Around them scientists from all over Mars ate and talked about the events of the morning. “We think it’s parts per billion.” “No, sulfates behave conservatively.” It sounded like the people at the table next to theirs were assuming there was going to be a shift to a two-phase model. One woman said something about raising the mean temperature to 295°K, seven degrees higher than Terra’s average.

Sax squinted at all these expressions of haste, of greed for heat. He saw no need to be dissatisfied with the progress that had been made so far. The ultimate goal of the project was not purely heat, after all, but a viable surface. The results so far certainly seemed to give no reason for complaint. The present atmosphere was averaging 160 millibars at the datum, and it was composed about equally of CO₂, oxygen, and nitrogen, with trace amounts of argon and other gases. This was not the mixture Sax wanted to see in the end, but it was the best they had been able to do given the inventory of volatiles they had to begin with. It represented a substantial step on the way to the final mix Sax had in mind. His recipe for this mix, following the early Fogg formulation, was as follows:

300 millibars nitrogen

160 millibars oxygen

30 millibars argon, helium, etc.

10 millibars CO₂ =

Total pressure at datum, 500 millibars

All these amounts had been fixed by physical requirements and limits of various kinds. The total pressure had to be high enough to drive oxygen into the blood, and 500 millibars was what was obtained on Earth at about the 4,000-meter elevation, near the upper limit of what people could live at permanently. Given that it was near the upper limit, it would be best if such a thin atmosphere had more than the Terran percentage of oxygen in it, but it could not be too much more or else fires might be hard to extinguish. Meanwhile CO₂ had to be kept below 10 millibars, or else it would be poisonous. As for nitrogen, the more the better, in fact 780 millibars would be ideal, but the total nitrogen inventory on Mars was now estimated at less than 400 millibars, so 300 millibars was as much as one could reasonably ask to put into the air, and perhaps more. Lack of nitrogen was in fact one of the biggest problems the terraforming effort faced; they needed more than they had, both in the air and in their soil.