Let's look at a real scientist and a hero.
James Hansen is a scientist and heads the Goddard Institute for Space Studies. He's been warning about global warming since 1988. Lately, he's turned militant like Fred Singer.
“The first GISS (NASA Goddard Institute for Space Studies) global temperature analysis was published in 1981. Hansen and his co-author analyzed the surface air temperature at meteorological stations focusing on the years from 1880 to 1985... Warming in the past century was found to be 0.5-0.7 °C, with warming similar in both hemispheres. When the analysis was updated in 1988, the four warmest years on record were all in the 1980s. The two warmest years were 1981 and 1987....
The temperature data was updated in 2006 to report that temperatures are now 0.8 °C warmer than a century ago, and conclude that the recent global warming is a real climate change and not an artifact from the urban heat island effect. The regional variation of warming, with more warming in the higher latitudes, is further evidence of warming that is anthropogenic in origin...
In 2003 Hansen wrote a paper called Can We Defuse the Global Warming Time Bomb? in which he argues that human-caused forces on the climate are now greater than natural ones, and that this, over a long time period, can cause large climate changes. He further states that a lower limit on “dangerous anthropogenic interference” is set by the stability of the Greenland and Antarctic ice sheets. His view on actions to mitigate climate change is that "halting global warming requires urgent, unprecedented international cooperation, but the needed actions are feasible and have additional benefits for human health, agriculture and the environment."
A year later, Hansen joined with Rahmstorf and colleagues comparing climate projections with observations. The comparison is done from 1990 through January 2007 against physics-based models that are independent from the observations after 1990. They show that the climate system may be responding faster than the models indicate. Rahmstorf and coauthors show concern that sea levels are rising at the high range of the IPCC projections, and that it is due to thermal expansion and not from melting of the Greenland or Antarctic ice sheets.
Following the launch of spacecraft capable of determining temperatures, Roy Spencer and John Christy published the first version of their satellite temperature measurements in 1990. Contrary to climate models and surface measurements, their results showed a cooling in the troposphere. However, in 1998, Wentz and Schabel determined that orbital decay had an effect on the derived temperatures. Hansen compared the corrected troposphere temperatures with the results of the published GISS model, and concluded that the model is in good agreement with the observations, noting that the satellite temperature data had been the last holdout of global warming denialists, and that the correction of the data would result in a change from discussing whether global warming is occurring to what is the rate of global warming, and what should be done about it.
In a paper published May 18, 2007, Hansen discussed the potential danger of "fast-feedback" effects causing ice sheet disintegration, based on paleoclimate data. George Monbiot reports "The IPCC predicts that sea levels could rise by as much as 59 centimetres (1.94 ft) this century. Hansen’s paper argues that the slow melting of ice sheets the panel expects doesn’t fit the data. The geological record suggests that ice at the poles does not melt in a gradual and linear fashion, but flips suddenly from one state to another. When temperatures increased to 2–3°C (3.6–5.4°F) above today’s level 3.5 million years ago, sea levels rose not by 59 centimeters but by 25 metres (82 ft). The ice responded immediately to changes in temperature."
Hansen stresses the uncertainties around these predictions. "It is difficult to predict time of collapse in such a nonlinear problem ... An ice sheet response time of centuries seems probable, and we cannot rule out large changes on decadal time-scales once wide-scale surface melt is underway." He concludes that "present knowledge does not permit accurate specification of the dangerous level of human-made [greehouse gases]. However, it is much lower than has commonly been assumed. If we have not already passed the dangerous level, the energy infrastructure in place ensures that we will pass it within several decades."
That's a real scientist. He's been on the right track since 1988.
Look at the chart. This is what science is about. You eliminate the null hypothesis.