movie review: 500 days of summer

This is primarily a movie about love.
It is also a movie about the dangers of global warming.
Set in a harrowing version of the near future in which Earth has been ravaged to the extent that summer blisters for 500 days, followed by a single day of frigid winter (a premise I found, from the beginning, somewhat preposterous), a boy and a girl meet when they are stationed at the same Water Rationing Facility (WRF) for their mandatory two years of civil service.
The boy, Tom, immediately falls for the girl, Summer (this name is apparently a coincidence unintended by the writers of the film). She resists his advances, believing that any previously 'normal' attempts at romantic relationships are irrelevant and obsolete given the current climate. He attempts to win her over, presenting her with his own rations of water and government-issued SPF 350 sunblock (and, in depriving himself, grows increasingly tan and dehydrated).
She finally agrees to go out with him on the sole evening of winter. They are both bundled in multiple layers of Gortex, their bodies completely covered even indoors to combat the chilling blasts of below-zero wind that can penetrate walls. They huddle in front of a massive fire, staring at each other through fur-lined goggles and practically yelling to be heard through enormous earmuffs. Tom confesses his feelings at length, and Summer, finally deciding to enjoy her life despite its bitter conditions, admits she cares for him too.
They peel back their mouth coverings. Their lips, exposed to the cold, immediately blister and blanch blue, ice crystals crackling at the corners. As they press their dry, shivering mouths together, Tom slumps back on to the couch. He is dead. After sharing his water rations with Summer for weeks, he has finally succumbed to dehydration.
At this point, several people around me in the audience were sobbing. I, however, remained unmoved. Why should his dehydration overcome him at the exact moment of his first kiss? And, if Summer really cared for him, wouldn't she have noticed that he had grown weaker and increasingly absentminded and stopped accepting his rations? It all seemed a bit far-fetched and emotionally manipulative to me.
The heat returns the next day and a disconsolate Summer reports to the WRF. Apparently, there are always a lot of casualties on the only day of winter and, in addition to Tom, about 20 other staff members have also died (many people, especially the elderly, simply can't withstand the extreme change in climate or die of exposure, lacking sufficient shelter). The government has therefore assigned a new set of trainees to the facility, one of whom, Ben, is immediately attracted to Summer.
And it begins again.
This film is an interesting take on the traditional romantic comedy, for sure, but a little dark for my taste.