I would like to know if modern CPU's automatically adjust their workload to current temperature
A CPU não pode ajustar sua carga de trabalho - cabe ao agendador do sistema operacional fazer isso.
O que a CPU pode (e vai) fazer é começar a reduzir suas freqüências operacionais quando a temperatura dos núcleos ficar muito alta.
If temperatures increase beyond Hot Scale, then ~ 5c below Tjunction Max, Throttling is activated. The Digital Thermal Sensors (DTS) are used to trigger Intel's TM1 and TM2 technologies for frequency, multiplier and Vcore Throttling within individual Cores. If Core temperatures increase further to Tjunction Max, then Shutdown occurs.
A partir desta folha de dados da Intel para o Core 2 Due (junho de 2009):
When Thermal Monitor 2 is enabled, and a high temperature situation is detected, the Thermal Control Circuit (TCC) will be activated. The TCC causes the processor to adjust its operating frequency (using the bus multiplier) and input voltage (using the VID signals). This combination of reduced frequency and VID results in a reduction to the processor power consumption.