Miami has a (humid) sub-tropical climate, that is characteristic of regions just north of the Tropic zone.  The subtropics in the Northern Hemisphere, start where the Tropics end at 23.5 degrees north at the Tropic of Cancer and extend roughly to 40 degrees north. As shown in the graph below, Miami falls right outside of the Tropic of Cancer with their precise Lat and Long being Miami: 25º 78' N, 80º 22' W.

Source:1

Source: 2

Features of a humid subtropical climate are year round warm weather, with little seasonal variation. They generally have, if any, days a year below freezing and receive abundant precipitation, mostly during the summer months. 

Miami Climate Graph - Florida Climate Chart

Source: 4

Above is a conglomerate of the average highs, lows, and precipitaion for Miami, Florida which illustrates how the city is an ideal archetype for a humid subtropical region. As shown above, the coldest average of the year is 76 degrees Fahrenheit while the warmest is slightly above 90 degrees Fahrenheit, which makes only a 15 degrees differential between the coldest and warmest month of the year. An archetypal example of a humid sub-tropical region. 

Bowen Ratio

Miami being adjacent to the Atlantic Ocean, as well as the Everglades which is mostly swampland and a vast watershed for the state, and the Gulf of Mexico only 80-100 west of the city, Miami has abundant water and therefore a large relative humidity as opposed to places within the interior of the country. 

Relative Humidity by Month (Percentage) Morning Jan. Feb. Mar. Apr. May. Jun. Jul. Aug. Sep. Oct. Nov. Dec. 84% 84% 82% 79% 80% 84% 83% 85% 87% 86% 85% 84% Afternoon 60% 57% 56% 54% 58% 65% 63% 65% 66% 63% 62% 60% Source:3

I would guess that Miami's Bowen Ration would be around 2:10 or .20 because of the abundant amount of water,  most of it will go toward latent heat exchange. 

Geebit Questions

Average Global Temperature: 58.9F

Albedo decrease by -10: 76.7F

Albedo increase by 10: 39.1F

Greenhouse increase by 10%:44F
Greenhouse decrease by -10%: 34.2F 


If the albedo were to increase and the planet was drastically warmer, I would suspect that more of the ice caps would melt and thus, Miami being barely above sea level, would probably be partially submerged underwater due to an increase in sea level. 

As for the other ones, Miami's overall temperature would fluctuate but nothing nearly as drastic as if the planet were to absorb more incoming radiation. Miami is already nearly 20F being situated near the tropics, warmer than the average global temp, therefore it would see remain warmer than most of the globe.  

Sources

1)"Humid Subtropics." Encyclopædia Britannica. Encyclopædia Britannica Online. Encyclopædia Britannica Inc., 2012. Web. 05 Mar. 2012.

2)"The World Factbook." CIA. CIA, n.d. Web. 8 Mar 2012. <https://www.cia.gov/library/publications/the-world-factbook/docs/refmaps.html>

3)"Miami Relative Humidity." City Rating. N.p., 2011. Web. 8 Mar 2012. <http://www.cityrating.com/cityhumidity.asp?City=Miami>.

4)"Climate-Miami-Florida." US Climate Date. US Climate Date, n.d. Web. 8 Mar 2012. <http://www.usclimatedata.com/climate.php?location=USFL0316>.