Complex sentence: The dogs are temporarily left behind, but the storm is worse than expected, and because of the harsh weather conditions and a shortage of supplies at the McMurdo Station, it soon becomes apparent that no rescue will be attempted until the next spring.
Split into simpler sentences: The dogs are temporarily left behind, but the storm is worse than expected. Because of the harsh weather conditions and a shortage of supplies at the McMurdo Station, it soon becomes apparent that no rescue will be attempted until the next spring.