I told her the story the Year Without a Summer, with two major snowstorms in June in New England and frosts in July. The year after Mount Tambora blew should have precipitated a new Ice Age.
But it didn't.
The global warming skeptics (i.e., oil company employees one way or another) all like to insist this proves warming and cooling are "natural" cycles totally unrelated to human effects.
I like to stand everyone else's arguments on their heads and say, if it wasn't for global warming, there would be a mile of ice above Manhattan. And Chicago. And Detroit. And we might all be back in our caves.
The reconstructions used, in order from oldest to most recent publication are:
1. (dark blue 1000-1991): P.D. Jones, K.R. Briffa, T.P. Barnett, and S.F.B. Tett (1998). "High-resolution Palaeoclimatic Records for the last Millennium: Interpretation, Integration and Comparison with General Circulation Model Control-run Temperatures". The Holocene 8: 455-471. DOI:10.1191/095968398667194956
2. (blue 1000-1980): M.E. Mann, R.S. Bradley, and M.K. Hughes (1999). "Northern Hemisphere Temperatures During the Past Millennium: Inferences, Uncertainties, and Limitations". Geophysical Research Letters 26 (6): 759-762. DOI:10.1029/1999GL900070 (pre-print)
3. (light blue 1000-1965): Crowley and Lowery (2000). "Northern Hemisphere Temperature Reconstruction". Ambio 29: 51-54. Modified as published in Crowley (2000). "Causes of Climate Change Over the Past 1000 Years". Science 289: 270-277. DOI:10.1126/science.289.5477.270 (data available from NCDC : )
4. (lightest blue 1402-1960): K.R. Briffa, T.J. Osborn, F.H. Schweingruber, I.C. Harris, P.D. Jones, S.G. Shiyatov, S.G. and E.A. Vaganov (2001). "Low-frequency temperature variations from a northern tree-ring density network". J. Geophys. Res. 106: 2929-2941. DOI:10.1029/2000JD900617
5. (light green 831-1992): J. Esper, E.R. Cook, and F.H. Schweingruber (2002). "Low-Frequency Signals in Long Tree-Ring Chronologies for Reconstructing Past Temperature Variability". Science 295 (5563): 2250-2253. DOI:10.1126/science.1066208
6. (yellow 200-1980): M.E. Mann and P.D. Jones (2003). "Global Surface Temperatures over the Past Two Millennia". Geophysical Research Letters 30 (15): 1820. DOI:10.1029/2003GL017814.
7. (orange 200-1995): P.D. Jones and M.E. Mann (2004). "Climate Over Past Millennia". Reviews of Geophysics 42: RG2002. DOI:10.1029/2003RG000143
8. (red-orange 1500-1980): S. Huang (2004). "Merging Information from Different Resources for New Insights into Climate Change in the Past and Future". Geophys. Res Lett. 31: L13205. DOI:10.1029/2004GL019781
9. (red 1-1979): A. Moberg, D.M. Sonechkin, K. Holmgren, N.M. Datsenko and W. Karlén (2005). "Highly variable Northern Hemisphere temperatures reconstructed from low- and high-resolution proxy data". Nature 443: 613-617. DOI:10.1038/nature03265
10. (dark red 1600-1990): J.H. Oerlemans (2005). "Extracting a Climate Signal from 169 Glacier Records". Science 308: 675-677. DOI:10.1126/science.1107046
11. (black 1856-2004): Instrumental data was jointly compiled by the Climatic Research Unit and the UK Meteorological Office Hadley Centre. Global Annual Average data set TaveGL2v  was used.
Documentation for the most recent update of the CRU/Hadley instrumental data set appears in: P.D. Jones and A. Moberg (2003). "Hemispheric and large-scale surface air temperature variations: An extensive revision and an update to 2001". Journal of Climate 16: 206-223. DOI:10.1175/1520-0442(2003)016<0206:HALSSA>2.0.CO;2
The flip side of my argument still holds: if we don't learn to control our excesses, the Gulf will extend north to the Missouri, Manhattan will be under three hundred feet of water, and who knows? Velociraptors or their reasonable facsimilies may end up stalking the swamps of Montana again .