If we are entering an ice age that may slow us RTWs down a bit, but if it is global warming coming, no problem, *just tape ice cubes to your wrists, this will cool your blood and the cooled blood will journey to all parts of your body and brain.
Also, resting in a hammock and gently swinging the hammock tends to lower body temperature by keeping the body at rest as opposed to exercising, and because of the slight movement of air created by the swinging hammock. It helps if you can find an assistant to attach a rope to the hammock and swing you in the hammock thus allowing you to remain even stiller, and in between swings, your assistant might replace the melted ice taped to your wrists with fresh ice. Remember not moving is the key, just stay calm and don't worry.
*leaned many years ago in hot and humid Puerto Limón, Costa Rica while serving as a U S Peace Corps volunteer,

Or, not finding anyone willing to help out, which is often the case, just attach a rope to a nearby tree - a few feet to one side or other of the hammock and swing yourself so the outbound swing of the hammock puts you within reaching distance of your catch of ice, usually some kind of ice chest, and you can scoop ice in a cupped hand without too much movement and then gently replace the melted ice under the wet tape on your wrists with the fresh ice. 9 out of 10 scientists agree this process cools the body below ambient temperatures if the ambient temperature is above 98.6 F. The one dissenting scientist was old school and no one really took him seriously anyway.
Hope this helps.

xfiltrate eat, drink and stay kool